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The Biopsychology of Healthy Eating

You probably know how to eat right. But do you know why?

Key points

  • Recent food neuroscience offers a new perspective on healthy eating practices and why we struggle.
  • Changes in the external food environment have widespread and profound effects on our biological appetite systems.
  • Changing our food environments and adopting nutrition patterns aligned with our appetite systems is the formula for metabolic health.

What do Dwight Eisenhower, Richard Nixon, and Willy Wonka have in common? If you guessed that all three played outsized, accidental roles in the modern U.S. obesity epidemic, you'd be right.

Ask the experts about the causes of obesity in America, and you will find no shortage of villains. Sugar. TV and video games. School lunch programs. Even air conditioning.1 And these experts would all be technically correct, in the same way, that a person jumping from an airplane without a parachute technically dies from the landing, not the falling. But to understand the "falling" behind the modern obesity epidemic, it turns out that a pair of Presidential misfortunes, combined with some extraordinary Hollywood imagination, offers possibly the best explanation according to the latest food neuroscience.2

In 1955, President Dwight D. Eisenhower unexpectedly suffered a heart attack. Although a heart attack affecting the world's most powerful person is a serious enough event on its own, the timing could hardly have been worse. Public health statistics pointed to soaring rates of heart disease in America during previous decades.

With heart disease now threatening U.S. leadership in ways no foreign enemy could rival, the public, politicians, and medical experts alike demanded answers. Enter Ancel Keys. The redoubtable Keys was at this same time completing some of the most ambitious studies to date concerning health and nutrition. Based on his data, Keys concluded that cholesterol and high-fat diets were the leading causes of rising rates of heart disease in the U.S. and Europe.

A government eager for applicable information, coupled with an outspoken scientist in Keys known for crushing researchers with incompatible views, thus became the first powerful domino of the modern obesity epidemic: nutrition became government policy, manifesting fully and irreversibly in 1977 in the Dietary Goals for the United States.3

By 1971, America had problems bigger even than heart attacks. Already struggling abroad with a massively unpopular war in Vietnam, President Nixon found himself simultaneously besieged at home by soaring food and sugar prices. Fighting for re-election, he instituted dramatic agricultural policy changes to stabilize food prices and reverse inflation through the mass production of corn.

Thus began the era of high fructose corn syrup, ubiquitous soft drinks, corn-fed farm animals, ballooning portion sizes, and mass-scale industrialized food production. Combined with the Eisenhower-era-born government nutrition policies promoting low-fat foods, ultra-processed, high carbohydrate foods rapidly saturated American supermarkets and restaurants.

Not coincidentally, 1971 was also the year that a low-budget film titled "Willy Wonka and the Chocolate Factory" was released to theatres. Derived from Roald Dahl's popular children's book of the same name from the 1960s, Willy Wonka's twisted genius took trending government nutrition policies and processed food concepts to absurd heights. Unending rivers of chocolate flowed in his Factory, everlasting gumballs were there to be enjoyed, as was ice cream in flavors that never melted.

It was a food paradise for the participating children–albeit one fraught with dangers. However, even the imaginations of Dahl and Willy Wonka could not foresee the extent to which the outlandish nutritional spectacle inside the Chocolate Factory would come to resemble the modern U.S. food environment.

Thomas Rutledge
Source: Thomas Rutledge

The figure above combines research from nutritional neuroscience with data from human laboratory trials to reveal how decades of systematic changes in our external food environment interacted with our brain-and-gut-based appetite biology to produce an epidemic of obesity and metabolic disease.

In brief, we understand weight and body composition changes result from how the food environment influences three interrelated appetite systems. The latter include:

  1. A hypothalamus-centered control center that regulates appetite and weight and metabolic changes at the level of the brain.
  2. Gut-level systems detect food volume (how much you've eaten) and chemically detect nutrient content (amino acids, fatty acids, and glucose).
  3. a hodgepodge of appetite hormones secreted by the brain, gut, organs, fat and muscle cells, and the gut microbiome that communicate between metabolic tissues and regulate metabolic activity within the tissues.

Coordinated in a concert of breathtaking complexity, these external and internal systems cause you to feel hungry and full, to crave and prefer specific foods, to be highly sensitive to and influenced by food cues in your environment, and to animate the consumption of certain foods with feelings of security, love, and pleasure. Perhaps curiously, the one thing your elaborate appetite machinery isn't particularly concerned about is your weight. Understanding this requires a little context.

Thomas Rutledge
Source: Thomas Rutledge

It is difficult to overestimate just how quickly our external food environment has changed relative to our internal appetite biology. For hundreds of millennia, homo sapiens and their ancestors evolved appetite systems optimized for nutritional scarcity, social eating rituals, and circadian meal cycles.

To survive, we needed to be constantly alert for food opportunities and adept at storing excess energy during rare times of abundance. Then, over the archeologically trivial span of 50 years across the 20th and 21st centuries, we metaphorically changed from eating regular, family meals at the Little House on the Prairie (eating primarily farm-raised whole food produce and animal products) to isolated, round-the-clock food consumption in a societal-scaled version of Willie Wonka’s Chocolate Factory (sugar-saturated, ultra-processed foods).

Give it about 250,000 more years, and your appetite biology will perhaps have time to catch up. In the meantime, the figure above connects healthy eating advice with which you are probably already familiar with the food environment and appetite biology systems discussed above. For some, connecting their nutrition behavior with their nutrition biology is an important insight and source of motivation.

Thomas Rutledge
Source: Thomas Rutledge

These recent changes in the food environment aren't just wreaking havoc with your waistline and appetite biology. As indicated by the figure above, they may also be contributing to the pattern of rising psychological and psychiatric distress that has occurred over the same period as the obesity epidemic.

Although it is oversimplified to attribute decades of decline in mental health in the U.S. to changes in food and eating practices alone, the data supporting a connection between nutrition and psychiatric function are simultaneously compelling.4 Perhaps, more importantly, they are also actionable and potentially reversible.


1. McAllister EJ, Dhurandhar NV, Keith SW, Aronne LJ, Barger J, Baskin M, Benca RM, Biggio J, Boggiano MM, Eisenmann JC, Elobeid M, Fontaine KR, Gluckman P, Hanlon EC, Katzmarzyk P, Pietrobelli A, Redden DT, Ruden DM, Wang C, Waterland RA, Wright SM, Allison DB. Ten putative contributors to the obesity epidemic. Crit Rev Food Sci Nutr. 2009;49:868–913.

2. Kevin D Hall, I Sadaf Farooqi, Jeffery M Friedman, Samuel Klein, Ruth J F Loos, David J Mangelsdorf, Stephen O'Rahilly, Eric Ravussin, Leanne M Redman, Donna H Ryan, John R Speakman, Deirdre K Tobias, The energy balance model of obesity: beyond calories in, calories out, The American Journal of Clinical Nutrition, Volume 115, Issue 5, May 2022, Pages 1243–1254,

3. United States, U. States, Congress, C., Senate, S., & Select Committee on Nutrition and Human Needs, S. Committee on Nutrition and Human Needs. (0000). Dietary goals for the United States.

4. Marx W, Moseley G, Berk M, Jacka F. Nutritional psychiatry: the present state of the evidence. Proc Nutr Soc. 2017 Nov;76(4):427-436. doi: 10.1017/S0029665117002026. Epub 2017 Sep 25. PMID: 28942748.