While researching some recent history on the timeline of food events,
I ran across the fact that the Food Pyramid wasn’t even created until 1992.

 This surprised me, because somehow in the vague recesses of my mind, it was something taught to me during the early 1950s in the lower grades of elementry school, and I thought I recalled it being the subject of discussion in an undergraduate sociology college class in the late 1970s. However, after a bit more research I learned the following information.

USDA Food Pyramid History

The USDA Food Pyramid has its origins in the practice of agricultural chemistry in the late 1800s. Wilbur Olin Atwater, Ph.D., an agricultural chemist who founded and directed the Office of Experiment Stations (OES) for the USDA, wrote the first dietary guideline,

Atwater was a researcher, and received government funds to build a large respiration calorimeter for studying human metabolism,

In 1902, Atwater published a USDA Farmer’s Bulletin which emphasized the importance of variety, proportionality, and moderation in healthful eating in the diets of American males. In his research, he determined that the calorie was a means to measure the efficiency of a diet. He calculated that different types of food produced different amounts of energy, and he stressed the importance of a cheap and efficient diet that included more proteins, beans, and vegetables, and to limit the intake of fat, sugar and other starchy carbohydrates.

1917, the first USDA food guide appeared. It was titled How to Select Foods and was written by Caroline Hunt, a nutritionist for the USDA. It ignored Dr. Atwater’s advice to limit fat and sugar intake, and instead emphasized newly discovered vitamins and minerals. Foods recommended came in 5 groups:

milk and meat
cereals
vegetables and fruit
fats and fatty foods
sugars and sugary foods

There were changes to this basic guide to help families during the wartime rationing, but it wasn’t until 1940, when the first "Recommended Dietary Allowances (RDA)" was released from the National Academy of Sciences, that the USDA changed its recommendations again.

In 1943, it created the National Wartime Nutrition Guide, and then revised it in 1946 as the National Nutrition Guide. This guide offered 7 food groups which supported the RDA requirements:

Milk and milk products
Meat, poultry, fish, eggs, beans, peas and nuts
Bread, flour and cereals
Leafy green and yellow vegetables
Potatoes and sweet potatoes
Citrus, tomato, cabbage, salad greens
Butter, fortified margarine

During this time, many other guides were issued with contradictory advice. In 1956, because of the confusion, the multiple food group recommendations were revised to the "Basic Four" recommendation. Serving size recommendations were also added and the revisions were published in a booklet titled Essentials of an Adequate Diet..Facts for Nutrition Programs. The 4 food groups in this document included:

Milk
Meat
Fruits and vegetables
Grain products

In 1967, CBS aired a documentary on TV, Hunger in America which reported the extent of hunger and malnutrition among low income groups in the United States. This show galvanized the American people into demanding the expansion of federal food assistance programs. In 1968, the Senate appointed Senator George McGovern to chair the "Select Committee on Nutrition and Human Needs" with the goal of wiping out hunger and malnutrition in the US.

By 1969, the committee had succeeded in wiping out the US malnutrition issue, but wanting to secure further funding, it began expanding into other areas of health and nutrition.

McGovern and several members of his staff had become familiar with the Ancel Keys' influence on the American Heart Association, which was proposing that fat and cholesterol consumption should be lowered for better heart health, even though the link between the two had never been proven in any scientific study. With this focus, the creation of today's USDA Food Pyramid began.

As Gary Taubes writes in his article The Soft Science of Dietary Fat:

"It was Senator George McGovern's bipartisan, nonlegislative Select Committee on Nutrition and Human Needs--and, to be precise, a handful of McGovern's staff members--that almost single-handedly changed nutritional policy in this country and initiated the process of turning the dietary fat hypothesis into dogma.”

In January 1977, after listening to the testimony of Ancel Keys and other doctors and scientists intent on promoting the unsupported Dietary Fat-Heart hypothesis, the Committee published the "Dietary Goals for the United States" recommending that all Americans reduce their fat, saturated fat and cholesterol consumption, and increase their carbohydrate consumption to 55-60% of daily calories."

Gary Taubes writes about this historic event:

“Then resident wordsmith Nick Mottern, a former labor reporter for The Providence Journal, was assigned the task of researching and writing the first "Dietary Goals for the United States." Mottern, who had no scientific background and no experience writing about science, nutrition, or health, believed his Dietary Goals would launch a "revolution in diet and agriculture in this country." He avoided the scientific and medical controversy by relying almost exclusively on Harvard School of Public Health nutritionist Mark Hegsted for input on dietary fat. Hegsted had studied fat and cholesterol metabolism in the early 1960s, and he believed unconditionally in the benefits of restricting fat intake..”

Upon release of the guidelines, the cattle, egg, and dairy industries went ballistic. Congress was telling people that animal products were bad for health!

The intense pressure from these industries forced the committee into revising the report in late 1977. But the damage had been done, and American meat, egg and milk consumption continued to fall.

Because the goals of this document were so different, the USDA did not adopt them at first. In 1980, the USDA partnered with the Health and Human Services department to issue the first edition of the Dietary Guidelines for Americans, which eventually became the USDA Food Pyramid.

During the 1980s, several other guidelines and reports were issued by various agencies. These included the Surgeon General’s Report on Nutrition and Health, and the National Research Council’s Diet and Health Report. Both reports were heavily influenced by the low fat proponents.

The USDA leaned heavily on these reports in the revision of its USDA Food Pyramid guidelines in the early 1990s. Interestingly, the actual graphic for the USDA food pyramid came from Sweden.  In 1988, several USDA scientists obtained copies of Sweden’s food pyramid at an international conference, and used it as a graphical basis for a new guideline in the US.

The result was the 1992 USDA Food Pyramid. This graphical depiction of the USDA’s guidelines has been the source of government food advice since then.

The USDA revised the food pyramid in 2010. The panel of "experts" advising the USDA were all proponents of the low fat, high carb diet. The research supporting a lower carb diet and reduced grain consumption was not reviewed, and the pyramid continues to recommend the products that benefit agricultural and food processing interests.

The latest development in the USDA Food Pyramid history saw the pyramid dismantled in favor of the new and "easier" to understand USDA "My Plate”

Although the graphic has changed, the same dietary advice is still being offered.

FOOD HISTORY TIMELINE

Here’s more history of food events between 1950 and 1982.

1951 The first Jack-in-the-Box opens in San Diego

1951 Swanson introduces beef, chicken, turkey pot pies.

1952 The first sugar free no calorie soft drinks are introduced.

1952 Lipton's dry Onion Soup Mix is introduced.

1952 Sugar Frosted Flakes, 29 percent sugar, are introduced by Kelloggs.

1952 Clarence Birdseye introduces the first frozen peas.

1952 Mrs. Paul's introduces frozen fish sticks.

1952 Colonel Harland Sanders begins to franchise KFC restaurants. Pete Harman of Salt Lake City gets the first franchise, and agrees to pay 5 cents for each chicken sold.

1953 USDA Agricultural Research Service created.

1953 John H. Kraft received a patent for the manufacture of soft surface cured cheese.

1953 Dow Chemical creates Saran Wrap

1953 The French Sardine Co. (since 1917) becomes Star-Kist Foods. Charlie the Tuna comes on board in 1961.

1953 Kraft Cheez Whiz is introduced. Originally created as an easy way to make Welsh rarebit, this stable cheese sauce comes in a jar with Worcestershire sauce, mustard flour and orange coloring added. A survey of American housewives reveals more than 1,300 possible uses for the product.

1953 Kellogg’s Sugar Smacks are introduced - they contained 56% sugar.

1953 Simplot introduced frozen french-fried potatoes on a commercial basis.

1953 There were more than 15,000 pizzerias in the U.S.

1953 The first Danny's Donuts opened in Lakewood California. The name will change to Danny's Coffee Shops, and finally in 1959 to Denny's Restaurants.

1954 TV dinners are introduced. C.A. Swanson & Sons introduced the first TV dinner: roast turkey with stuffing and gravy, sweet potatoes and peas. It sold for 98 cents and came in an aluminum tray, so you could just open the box and heat the dinner in the oven. (No microwave ovens back then). Supposedly executive Gerald Thomas came up with the idea when the company had tons of leftover turkey from Thanksgiving. The idea for the aluminum trays came from the trays used for airline food.. They were an immediate success, and Turkey dinners are still the most popular Swanson frozen dinner. Swanson stopped calling them TV dinners in 1962.

1954 Carnation introduced instant nonfat dry milk.

1954 Kraft introduced Cracker Barrel brand natural cheese.

1954 Process for making instant potato flakes developed.

1954 The Butterball brand and the self-basting turkey are introduced. Through genetics, Swift develops a broad-breasted bird without the tough tendons and uses a hot-water bath to remove feathers.

1954 M&M's Peanut Chocolate Candies were introduced. Also, the the famous slogan, 'The milk chocolate melts in your mouth, not in your hand,' slogan is introduced.

1954 Trix cereal is introduced by General Mills. It is more than 46% sugar.

1955 First franchised McDonald's was opened in Des Plaines, Illinois, by Ray Kroc, who bought the hamburger restaurant owned by the McDonald brothers. On opening day a 2 patty hamburger was 15 cents and French Fries were 10 cents.

1955 Disneyland opened in Anaheim, California.

1955 The U.S. minimum wage was raised from 75 cents to $1.00

1955 The first microwave oven for home use was introduced by the Tappan Stove Company. It cost about $1,300.

1955 Kellogg introduced Special K breakfast cereal, with only 4.5% sugar.

1956 80% of U.S. households now have a refrigerator.

1957 Burger King introduced the Whopper burger.

1957 Better Homes & Gardens prints its first microwave-cooking article.

1957 Margarine sales exceed butter sales for the first time.

1957 General Foods Corp. introduces TANG breakfast beverage crystals.

1957 Kentucky Fried Chicken begins selling chicken in buckets.

1958 Friskees introduced the first dry cat food

1958 Rice-A-Roni goes on sale.

1958 Cocoa Puffs cereal is introduced by General Mills; it contains 43% sugar.

1958 Cocoa Krispies is introduced by Kellogg’s - it's 45.9% sugar.

1958 Jolly Green Giant was born. He appears on TV, but he looks like a monster and scares kids. So they lighten him up a bit, added 'Ho, ho, ho' and and a catchy jingle.

1958 Sweet n' Low was introduced as an artificial sweetener.

1958 McDonald's sold its 100 millionth hamburger.

1958 Jif peanut butter was introduced (creamy).

1958 Royal Crown Cola begins test marketing Diet Rite Cola, the first diet cola. It goes national in 1962.

1959 The one billionth can of Spam was sold

1959 Polish born New York businessman Reuben Mattus created a premium ice cream. He gave it the Danish sounding name, Haagan Dazs.

1959 Mike Ilitch opened the first 'Little Caesars Pizza'

1960 Frozen bagels were introduced.

1960 Instant potatoes developed.

1960 Aluminum cans were first used commercially for food and beverages.

1960 Domino's Pizza was founded.

1961 'Boiling Bags' were introduced - frozen plastic packages of food that can be dropped in boiling water to heat them for serving.

1961 Teflon coated frying pans were introduced.

1961 General Mills introduced 'Total' breakfast cereal.

1961 Unilever introduced 'Mrs. Butterworth's Syrup.

1961 Green Giant entered the frozen food business with peas, corn, green beans and baby Lima beans in pouches with butter sauce.

1961 Coca-Cola Co. introduced 'Sprite' lemon-lime soft drink to compete with 7-Up.

1961 Carnation introduced 'Coffee-Mate' nondairy creamer.

1962 The pull tab for beverage cans is introduced.

1962 Planters introduced dry roasted peanuts.

1963 Maxwell House introduced the first freeze-dried instant coffee.

1963 Jean Nidetch founded Weight Watchers.

1963 Fruit Loops breakfast cereal is introduced.

1963 ChipsAhoy! chocolate chip cookies are introduced.

1963 The one billionth McDonald's hamburger was served by Ray Kroc on the Art Linkletter Show.

1963 Coca Cola introduced TaB, its new diet cola.

1964 St. Paul, Minnesota gets its first McDonald's Restaurant. Burgers are 15 cents each.

1964 The first 12 oz aluminum can was introduced by Royal Crown Cola. It wasn't until 3 years later that Coke started using the aluminum can.

1964 Pepsi Cola introduced Diet Pepsi.

1965 Cool Whip, a whipped cream substitute, was introduced by General Foods. Within 3 months it is the top selling whipped topping product.

1965 The first Subway sandwich shop opens in Bridgeport, Connecticut.

1965 Campbell Soup Company introduces Franco-American Spaghetti-O's.

1965 The Pillsbury Doughboy, 'Poppin' Fresh,' was born. He made his debut in a commercial for crescent rolls.

1966 McDonald's begins using frozen french fries.

1966 Ingredients are required to be listed on food packages. The first Truth in packaging law.

1966 American Roman Catholics are no longer required to abstain from eating meat on Fridays.

1967 Gatorade, the original sports drink, is developed by the University of Florida for their football team.

1967 Plastic milk bottles are introduced.

1967 A gallon of milk cost $1.03, but in 2006 dollars that would be $6.24

1967 Wholesome Meat Act passed

1968 The Big Mac was introduced at McDonalds for 49 cents

1968 The first Red Lobster restaurant opened in Lakeland, Florida.

1969 Pringles potato chips were introduced - made from dehydrated, mashed potatoes.

1969 The last issue of the Saturday Evening Post was published. 1821-1969

1969 The 3 day Woodstock Music and Arts Fair began on a dairy farm in Upstate New York.

1969 Cyclamate, a non-caloric sweetener, was banned. Discovered in 1937, and widely used in the food industry, gigantic amounts of cyclamate were found to cause cancer in laboratory rats. Cyclamate is still used in many countries around the world.

1970 Hamburger Helper was introduced.

1970 The Red Lobster restaurant chain was acquired by General Mills.

1971 The Quarter Pounder was introduced at McDonald's for 53 cents.

1971 The first Starbucks opened in Seattle.

1971 Coca Cola introduces the plastic bottle.

1971 Disney World opened at Orlando, Florida.

1972 The McDonald's Egg McMuffin breakfast sandwich was created.

1972 The first Ruby Tuesday restaurant was opened near the Knoxville campus of the University of Tennessee.

1973 'Promise' brand margarine was introduced.

1973 'Stove Top Dressing' was introduced by General Foods.

1973 'Cup o'Noodles' was introduced in the U.S. by Nissin Foods.

1973 Coleman's Mustard celebrates its 150th anniversary.

1974 Nutrition labeling of fluid milk products begins.

1976 There are no red M&Ms from 1976 to 1987. The popular food coloring, Red Dye No. 2, was banned by the FDA because studies had shown it might cause cancer. Red M&Ms disappeared for 11 years because of the ban.

1976 Pierrier water was introduced in the U.S.

1978 Ben & Jerry’s Homemade Ice Cream and Crepes opened in a former gas station in Vermont.

1979 Pillsbury acquires the Green Giant Company.

1979 McDonald's introduced the Happy Meal for kids.

1979 General Mills introduced 'Honey Nut Cheerioes'

1979 There are about 6,000 KFC (Kentucky Fried Chicken) restaurants, and they sell 2.7 billion pieces of chicken.

1980 Due to record high sugar prices, Coca Cola begins substituting high fructose corn syrup for half of the sucrose (sugar) used in Coca Cola.

1980 McDonald's test marketed Chicken McNuggets in Knoxville, Tennessee. They are so popular that they have to look for a second supplier.

1981 Lean Cuisine frozen dinners were introduced.

1981 The USDA announced that ketchup could be counted as a vegetable in the school lunch program.

1981 The FDA approved the artificial sweetener Aspartame (NutraSweet) for tabletop use.

1982 Diet Coke was introduced.

Check out McDonald's original prices.



Here are a few food-related-events occuring over a past 50 year period.

1950’s – USDA creates four basic food groups: milk, meat, fruits and vegetables, and breads and cereals.

1954 – Swanson unveils the first TV dinners.

1955 – Ray Kroc opens his first McDonald’s franchise.

1963 – Weight Watchers is incorporated and the first public meeting is held in a loft in Queens.

1967 – Amana introduces the first domestic Radarange microwave oven.

1977 – Portion sizes start to swell. Hamburgers expand by 23% in the next 20 years; a plate of Mexican food gets 27% bigger; soft drinks increase by 52%; snacks (potato chips, pretzels, crackers) grow 60%.

1989 – February is declared National Snack Food Month by the Snack Food Association. A month-long campaign results in a 41% increase in snack food consumption.

1990s – Foods labeled “Low-Fat” and “Lite” hit their stride.

1991 – The World Wide Web is born.

1992 – USDA Food Pyramid is created.

1998 – Olestra, a non-digestible, nutritionless fat substitute is approved by the FDA for use in no-fat snacks.

What IS a good Diet (or Lifestyle or Way-of-Eating)?
What’s the criteria we use when making this judgment call?

Is it the amount of weight we lose, when we’re following it?
Is it the amount or the kind of food we eat, when we’re following it?
Is it the physical feeling our body has, when we’re following it?
Is it the emotional satisfaction we feel, when we’re following it?
Is it the length of time we can follow it?

 Here’s one answer:

How do you know you're on a "good" diet?

Simple. You like it.

What do I mean?

Tolerating a diet's not good enough.
If you're only tolerating your new lifestyle you're certainly not likely to keep living it.

Food wise - you can't be regularly battling hunger, it can't be making you feel unwell
and your life has to be "normal" meaning you should be able to include food
for comfort, food for celebration, with no forbidden foods.

Fitness wise -
you can't be running out of time, running out of energy, hurting yourself, or hating it.

Ultimately you're aiming for a lifestyle where you can't happily eat any less
and you can't happily exercise any more.

Sure we can all improve our lifestyles but to use an extreme example,
... do you really think you can be a tee-totaling vegan, shut-in, marathon runner forever?

If you can't happily eat less, you're not going to eat less.
If you can't happily exercise more, you're not going to exercise more.

Your goal should be your personal best
recognizing that the best lifestyle you can enjoy
and the best lifestyle that you can tolerate
are two very different things.

            Yoni Freedhoff, MD, Canadian obesity doctor, weightymatters .com

The basic truth of weight-loss is that one must figure out a way to somehow live with eating less than one wishes. This can be accomplished in many different ways. Most “Experts” have developed their own ideas about what works best, and they don’t hesitate to share them with us.

The concepts of losing weight are relatively easy when compared to the implementation of the eating-or-not-eating methods that are required to actually lose weight and to maintain that weight-loss.

But “easy” isn’t simple, and not only do the “experts” disagree on many weight-loss concepts, each of them has an agenda, a belief, about what is the “correct” way to implement weight-loss eating. Many times these “expert” beliefs oppose each other.

Articles by “experts” contain basic facts mixed with possibilities, and this combination is mixed with opinion. One problem for people with weight-problems is that it is almost impossible for us to separate FACT from THEORY from OPINION. Often the reasoning of an “expert” can seem very convincing .. but once we actually try to implement an individual eating solution an “expert” proposes, we find it to be personally unworkable.

Although I find the “WHY” to be interesting, it is basically useless to me unless the “HOW” is something I can accomplish long-term.  We aren't all the same, and each of us must figure out our own individual solution.

Most “experts” start with basic FACTS, and then move on to various THEORIES, and then move on to their own OPINIONS. Here at DietHobby, I often post copies of articles which I find personally interesting, and which offer solutions that might be workable for some. This doesn’t mean that I accept or agree with every Theory that is proposed in every article that I post here in DietHobby. It also doesn’t mean that I find that particular Solution to be workable for me, personally.

Here’s an interesting article by an “expert” who is an advocate of reducing the “reward” value of the food one chooses to eat.

Seduced by Food: Obesity and the Human Brain
                by Stephan Guyenet

In 1960-1962, the US government collected height and weight measurements from thousands of US citizens. Using these numbers, they estimated that the prevalence of obesity among US adults at the time was 13 percent. Fast forward to the year 2007-2008, and in the same demographic group, the prevalence of obesity was 34 percent . Most of this increase has occurred since 1980, when obesity rates have more than doubled among US adults, and extreme obesity has more than tripled. Welcome to the ‘obesity epidemic’. Today, more than one third of US adults are considered obese, an additional third are overweight, and largely as a consequence, each child born today has an estimated one in three risk of developing diabetes in his or her lifetime.

Since the obesity epidemic is a serious threat to public health and well-being, scientists have made it a research priority, and our understanding of its causes and consequences is rapidly expanding. Obesity can be the result of many interacting factors, including genetic makeup, developmental factors, physical inactivity, stress, insufficient sleep, social factors and smoking cessation. But dietary changes are clearly an outsized contributor. The obesity epidemic has closely paralleled a large (~20%) increase in per capita calorie intake, and according to the best available mathematical models, this increase can single-handedly account for the increase in body fatness over the last 30 years

Calories are interesting, but let’s delve deeper. We didn’t just wake up one day and decide to eat more—something is driving our increased food intake. But what? Research accumulated over the last two centuries has revealed that the answer lies in the intricacies of the human brain.

The Human Brain and Obesity

In 1840, a German doctor named B. Mohr made a critical observation while performing autopsies on obese subjects: some of them had damage in a part of the brain called the hypothalamus (B. Mohr. Wschr Heilkd, 6:565–574. 1840). Over the ensuing century and a half, researchers gradually uncovered a network of circuits in the hypothalamus dedicated to maintaining the stability (homeostasis) of body fat stores, by regulating food intake, energy expenditure, and the deposition of energy in fat tissue. This research culminated in the discovery of an extraordinary hormone called leptin in 1994. Produced by fat tissue in proportion to its mass, leptin enters the circulation and acts in the hypothalamus to regulate body fat stores. If you consistently restrict food intake, fat mass declines and so does leptin, and this signals the hypothalamus to stimulate hunger and make the body use calories more efficiently, in an attempt to regain lost body fat . Conversely, if you consistently overeat, the increase in fat mass and leptin suppresses appetite and increases calorie use until body fat stores have declined back to baseline. Leptin and a few other hormones are part of a negative feedback loop that acts unconsciously to keep fat mass in a specific range, sort of like a thermostat does for temperature. This is called the ‘energy homeostasis system’.

So if we have this built-in system to regulate body fatness, how does anyone become obese? Some researchers believe the energy homeostasis system defends against fat loss more effectively than fat gain. However, most obese people regulate their body fat just fine, but their brains ‘defend’ it at a higher level than a lean person. Going back to the thermostat analogy, in obese people it’s like the ‘temperature’ has been gradually turned up. That’s why it’s so hard to maintain weight loss—when body fat stores decline, the brain thinks it’s starving even if fat mass remains high—and it acts to regain the lost fat. If we want to understand how to prevent and treat obesity, first we have to understand why obese people defend a higher level of fat mass than lean people.

The most Fattening Diet in the World

To understand how this happens, let’s turn to animal research. Although rodents aren’t humans, they resemble us in many ways. Just like humans, rodents evolved to regulate body fat around an ‘optimal’ level to maximize survival and reproduction, and their systems for doing this are very similar to ours. Rodents also offer us the ability to control variables much more tightly than in human research. There are many ways to make a rat obese, but some are more effective than others. High-fat pelleted diets, composed of refined ingredients, are most common because they’re reliably fattening and their composition can be tightly controlled. But another diet, seldom used, is the most fattening of all: the ’cafeteria diet’. This diet has a lot to tell us about the expanding American waistline.

First described in 1976 by Anthony Sclafani, the cafeteria diet is basically a rat-sized buffet of human junk food, in addition to regular rat chow. The menu for a recent cafeteria diet study included such delectable items as Froot Loops, mini hot dogs, peanut butter cookies, Cheez-its, Cocoa Puffs, nacho cheese Doritos, cake, and BBQ pork rinds. These are what's known in the business as ‘palatable’, or pleasurable to the taste. On this regimen, rats ignored their regular chow, ate junk food to excess and gained fat at an extraordinary rate, far outpacing two comparison groups fed high-fat or high-sugar pelleted diets. Yes, human junk food happens to be the most effective way to overwhelm the body fat homeostasis system in rats, and neither fat nor sugar alone is able to fully explain why it’s so fattening. Importantly, over time, rats become highly motivated to obtain this diet—so motivated they’ll voluntarily endure extreme cold temperatures and electric shocks to obtain it, even when regular bland rodent pellets are freely available.

The cafeteria diet is an exaggerated version of an unhealthy human diet, and not many people eat quite that poorly. However, have a look at the top six calorie sources in the current US diet, in order of calorie contribution: grain-based desserts (cake, cookies, etc.), yeast breads, chicken-based dishes, sweetened beverages, pizza and alcoholic beverages. Our eating habits aren’t as different from the cafeteria diet as we might like to believe.
In 1992, Eric Ravussin and collaborators tried to repeat the rodent experiment in humans. They gave volunteers unlimited access to a large variety of palatable energy-dense foods, in a setting where the researchers could monitor exactly what was eaten. Over the course of the next week, the volunteers more than doubled their usual calorie intake, gaining an average of five pounds. Further studies showed a similar effect. Just as in rats, exposing humans to a large variety of palatable energy-dense foods causes an increase in food intake and rapid fat gain. To explain this, we need to bring our attention back to the brain.

My Neurons Made Me Fat

To understand why junk food causes fat gain in rats and humans, we have to explore two other circuits in the brain, beginning with the reward system. The reward system acts to gauge the desirability of food (among other stimuli) and reinforce and motivate behaviors that favor the acquisition of desirable food. For example, if you eat a strong cheese for the first time, maybe it won't taste very good to you. As it's digested, your reward system gets wind that it's full of calories, and the next few times you eat it, it tastes better and better until you like the flavor. This is called an acquired taste, and the reward system is what does the acquiring, motivating you to obtain a food it has deemed safe and desirable. This is the same process that allows children to learn to like vegetables—which are low-calorie, often bitter foods that are initially unpalatable-- if they’re repeatedly paired with fat, salt or some other desirable quality. The reward system does the same thing with foods/beverages that contain drugs, such as coffee and beer, gradually making bitter fluids palatable and then delicious.

Eventually, you may go out of your way to purchase the cheese or beer at the grocery store, and maybe you'll consume cheese or beer even if you aren't hungry or thirsty, simply because you like it. This is an example of the reward system reinforcing and motivating behaviors related to foods it considers desirable. What does the reward system consider desirable? Calorie density, fat, starch, sugar, salt, free glutamate (umami), certain textures (easily chewed, soft or crunchy, solid fat), certain flavors, an absence of bitterness, food variety, and drugs such as alcohol and caffeine. Our brains are highly attuned to these qualities because they’re all elements of nutritious, calorie-dense foods that would have sustained our ancestors in a natural environment, but today, the exaggerated combinations of these qualities used by processed food manufacturers, chefs and sometimes even home cooks overstimulate our natural reward pathways. Commercial foods are professionally designed to maximize reward, because reward is precisely what keeps you coming back for more. Processed junk foods such as ice cream, fast food, sweetened soda, cookies, cake, candy, pizza and deep fried foods are all archetypal hyper-rewarding foods.

Palatability is a related concept—it’s determined in part by inborn preferences (e.g., a taste for sugar and energy dense foods), and in part by the reward system (acquired tastes). Palatability is governed by the hedonic system in the brain, which is closely integrated with the reward system. Imagine yourself sitting at the dinner table, stuffed after a large meal. Then the cake and ice cream appear, and suddenly you have enough room left for another 250 calories of food. Would you have eaten a large, unseasoned baked potato (250 calories) if someone had put one in front of you at that point? Foods that stimulate the hedonic system have a well known ability to increase food intake, and this effect can be replicated using drugs that activate these circuits directly. The reward system is what motivates you to get food and put it to your lips, every time you eat. When scientists shut it down in mice, they stop seeking food, even though they’ll still eat if it’s put into their mouths. The hedonic system influences how much you eat once you begin a meal.

Together, reward and hedonic circuitry in the brain determine in large part how often you seek food, what foods you select, and how much you eat at a sitting.

Reward and hedonic systems, if stimulated in the right way by food or drugs, can increase food intake and body fatness. The marijuana ‘munchies’ (whose existence have been confirmed by science) are a good example of what happens when they’re chemically stimulated via the CB1 cannabinoid receptor in the brain. One of the most effective weight loss drugs ever developed, Rimonabant, is basically ‘reverse marijuana’, blocking the very same CB1 receptor that marijuana activates. Although it clearly reduces food intake and body fatness, it has failed to gain FDA approval because of negative psychological side effects (big surprise).

The ability of reward and palatability to influence food intake and body weight is mediated by connections between reward/hedonic and energy homeostasis systems. For example, if you haven’t eaten in a while, your brain detects declining energy stores and acts to increase food intake. It does this by increasing your motivation to obtain food, and your enjoyment of food once you obtain it— known as ‘hunger’, this sensation is caused in large part by energy homeostasis systems activating reward and hedonic systems. But the connection goes both ways. Reward and hedonic systems also influence energy homeostasis systems, such that excessively rewarding/palatable food can increase food intake and the level of body fat that’s ‘defended’ by the brain. According to findings from my own research group (lab of Michael W. Schwartz) and others, the hypothalamus can also develop inflammation and chronic cellular damage that likely contributes to the defense of a higher fat mass as well, contributing to fat gain and making fat loss more difficult, but the reason for this is not yet clear.

Addiction is what happens when the reward system is over-stimulated by drugs, sex, food or other high-reward stimuli. In susceptible people (about 3 percent of the US population), highly palatable/rewarding foods are quite literally addictive, leading to binge eating behavior. For the rest of us, these foods may not literally be addictive, but they do often drive us to eat them more than we think we should, despite negative consequences to our weight and health.

Living in a Toxic Food Environment

How has the American diet changed over the years, as obesity rates have soared? Taking a broad perspective, the largest change is that our food has become more like the ‘cafeteria diet’, awash in a large variety of packaged foods, restaurant meals and sweetened beverages.

Diet trials have shown that a ‘simple’ diet, low in palatability and reward value, reduces hunger and causes fat loss in obese humans and animals, apparently by lowering the ‘defended’ level of fat mass. This may be a reason why virtually any diet in which food choices are restricted (e.g., Paleo, vegan, fruitarian), including diametrically opposed approaches like low-fat and low-carbohydrate diets, can reduce food intake and body fatness in clinical trials. As stated by Nora Volkow, director of the National Institute on Drug Abuse, “The common denominator of such diets is that neither allows consumption of the very caloric and seductive foods that combine high fat with high carbohydrates”. Hyper-rewarding/palatable foods—candy, chocolate, ice cream, chips, cookies, cakes, fast food, sweetened beverages and pizza—are uniquely fattening and should be the first foods to go in any fat loss attempt. Some people will benefit from further simplifying the diet.

Dietary changes over the last several decades have contributed to the obesity epidemic. The solution to this problem is at once simple and challenging. Returning to a diet of simple home-cooked food, made from minimally refined ingredients, would probably stop the obesity epidemic in its tracks, although it would not be enough to return all currently obese people to a lean state. The challenge is finding the time and discipline to do this while commercial junk foods and sweetened beverages are tasty, cheap and constantly under our noses.

Stephan Guyenet is an obesity researcher at the University of Washington in Seattle. He writes about nutrition and health at his blog Whole Health Source.