What environmental and food industry changes coincided with the obesity epidemic starting in the 1970s?
The Short Answer
Around 1980, obesity rates began rising sharply after being stable for decades. This coincided with multiple changes: the introduction of high-fructose corn syrup, the low-fat diet recommendations, the explosion of processed and fast food, increased food marketing, larger portion sizes, and the shift to eating more meals away from home. That these things changed is documented; that they caused the curve, alone or together, is not, and which of them did the work is less settled than the story usually told.
Something to Sit With
Human genetics didn’t change in 1980. The environment did.
What changed around you may explain what changed within you.
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The timeline. By the usual US survey figures, given here as general background, obesity rates stayed relatively stable from 1960 to 1980, around 15 percent of the population. Then, approximately:
- 1980: ~15% obesity rate
- 1990: ~23% obesity rate
- 2000: ~31% obesity rate
- 2010: ~36% obesity rate
- Today: ~42% obesity rate
(Those are the widely reported national survey figures. The survey itself is not in hand, so treat the shape of the curve as sound and the individual percentages as approximate.)
Something changed around 1980, and human genetics don’t shift that fast. What follows is the honest version of the argument this page makes: several things did change in that window, and it is established that they changed; it does not hold that they caused the curve. Portion sizes, for instance, began expanding in the 1970s, increased sharply in the 1980s, and parallel rising obesity rates.[1] A parallel is what that is. Reading a cause into it is the step the evidence doesn’t take, and this page is going to name each factor without taking it.
What changed. Multiple factors converged:
High-fructose corn syrup (1970s). HFCS became cheap and ubiquitous through corn subsidies and food science, entered sodas in 1984, and spread widely. (The rise in liquid sugar over this period is not a sourced figure. Take it as background rather than as measured.)
Low-fat dietary guidelines (1977-1980). The 1980 Dietary Guidelines did focus on reducing fat rather than sugar.[2] That much is documented. What followed is commonly attributed to them and not demonstrated by anything on this page:
- Increased carbohydrate consumption to replace fat calories
- “Low-fat” processed products with added sugar
- Demonization of fat while ignoring sugar’s role
Processed food explosion. Food science created increasingly palatable products:
- Combinations of fat, sugar, carbohydrate, and sodium that meet a quantitative definition of hyper-palatable food, met by 62% of the foods in one US food database[3]
- Extended shelf life
- Widespread availability and marketing
Portion size inflation. Servings grew larger:
- Fast food portions grew
- Restaurant portions expanded
- Packaged food “single servings” grew
Eating frequency increased. From three meals to constant eating:
- Snacking normalized
- Food available everywhere, constantly
- “Don’t skip meals” messaging
Food marketing intensified. Food advertising expanded over the same decades, children included. (Also general background, not a figure.)
Meals shifted out of home. More restaurant meals, more fast food, less home cooking.
The environment story. None of these factors is shown to explain the epidemic, alone or together. What they did create is an environment where:
- Highly palatable food is constantly available
- Portions are oversized
- Eating frequency is high
- Sugar is ubiquitous
- Dietary advice targeted fat rather than sugar
- Marketing constantly encourages consumption
This environment is recent. The brain that seeks calorie-dense food under scarcity evolved without it and has not changed to meet it.[4]
The implication. On this page’s reading, the obesity epidemic is less about individual willpower than about humans, unchanged biologically, placed in an environment radically different from anything in human history. The environment changed; bodies responded as bodies do.
Further reading:
- Guyenet SJ, The Hungry Brain[5] (2017) — The changing food environment
- Moss M, Salt Sugar Fat[6] (2013) — Food industry practices
- Cutler DM, Glaeser EL & Shapiro JM, “Why have Americans become more obese?”[7] — Journal of Economic Perspectives, 2003
- Nestle M, Food Politics[8] (2013) — How food policy shaped the epidemic
Written by AI, directed and approved by me. How this is made →