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Obesity: What happened in 1978?

An open letter to food and nutrition professionals

What happened?

The graph above shows a catastrophic event happened in the US around 1978.  After hundreds (probably thousands) of years of self-regulating body weight, Americans began, rather suddenly, to consume more calories than they needed, and gain weight.  What happened, but more importantly why?

First, where did those extra calories come from?  From this graph it is pretty clear, many of them came from a huge increase in the consumption of vegetable oils (purple line).  Vegetable oils were (and still are) promoted as being healthier than saturated fats from animal sources.  But over time, vegetable oils have not only replaced animal fat, but surpassed previous consumption (green line total fat).  And, with 9 calories per gram, oils contribute many more calories than the carbohydrates and proteins they would have displaced.  Like many foods, vegetable oils are not necessarily bad for you, just too much of a good thing.

Another big change was that Americans increasingly began eating “food away from home” – mostly in fast food restaurants (see graph at left from USDA Economic Research Service).  Clearly, much of this food is high in fat and calories.  Also in the late 70’s, the peak of the baby boomer generation entered the workforce, with more women working than ever before.  At the same time, home economics classes, which once taught nutrition and cooking skills, disappeared from American schools.  The result has been two generations of consumers with limited cooking skills (and dependent on prepared foods).

Added to that, the post-war prosperity that was once shared, began its long ascent to be concentrated in the top 95th percentile (graph at right reference).  It is little surprise that, with men and women both working, limited cooking skills, and real wages stagnated, low cost fast and prepared food became popular.  Possibly to increase the value perception, serving sizes ballooned as well.

On the other hand, ample fast food, junk food and soda pop existed before 1978 (See more here).  But Americans were able to maintain consistent weight.  Why did the “set-point” move?  Why did Americans start eating more than they needed, when they didn’t before?

many theories

There have been many theories: too much fat, too much sugar, too much salt, too much saturated fat, too little exercise, too many carbs, not enough carbs, not enough fruits and vegetables, and “hyper-palatable” processed foods with artificial ingredients.  It is clear that there are many foods in the American market that are high in calories but low in nutrients.  But what, exactly, is it about these foods that makes people eat more than they need?

In response to the obesity epidemic, many health-promoting public health measures have been proposed – and accomplished.  

As recommended, since 1970, Americans today consume less saturated fat, less red meat, fewer potatoes, more poultry, more vegetable oil, more dietary fiber, and more vegetables.  In the past 20 years, consumption of grains and added sweeteners have decreased. (See USDA and Pew research).  Dangerous trans fats have been eliminated.  And environmental hazards like indoor smoking and leaded gas are gone.  Yet, by most measures, Americans are more unhealthy than ever.  

So far, dietary changes have been unable to slow the increase in calorie consumption or obesity.  As a country, and increasingly the world, we seem to have lost the ability to control the most basic of human activities: eating.  What’s going on?

Maybe it's something besides the food

All agree the nutritional quality of foods for Americans needs improvement.  And clear, factual nutrition education and culinary training for consumers is badly needed.  But, could other things be going on?  Do we need to look beyond food?

Let us consider three other factors.  They have received less attention and research.  But they also coincide with our 1978 timeline and the demographics of obesity.  More importantly, these are factors that exercise, dietary or food formulation changes themselves cannot fix.

  • Normalization
  • Fast food packaging and nonstick cookware
  • Antibacterial soaps and other antimicrobials.


In the 1950’s and 60’s, being lean and physically fit was considered part of national readiness.  Presidents Eisenhower and Kennedy, concerned that “soft Americans” would “destroy the vitality of a nation“, instituted the Presidential Fitness Test.  Height/weight charts were prescriptive and regularly consulted.  If a person was overweight, their doctor would advise them to cut back on their eating.

Now our attitudes are more inclusive, compassionate and less rigid, taking into account individual differences.  In addition, as the obesity epidemic has progressed, obesity is no longer novel.  In many communities it is the norm.  According to Harvard, the chances of becoming obese go up 57% if a friend is obese.

In the face of this prevalence (and in some cases acceptance), advise on diet and exercise may seem unnecessary (and unwelcome).  Furthermore, many have developed negative associations with eating, which further dietary advice will only exacerbate.   As the Obesity Society points out “Bias and stigmatization directed at people with obesity contributes to poor health and impairs treatment”.  This is a very complicated societal (and only partly dietary) challenge.  How can we, as a society, get back to enjoying appropriate amounts of food again?

Obesogens - Fast Food Packaging and Nonstick cookware

As this article describes, scientists have discovered chemicals that, in animal studies, cause obesity.  Called “obesogens”, they can affect both the size and number of fat cells.  Animals exposed to obesogens during development become obese adults.  

Many chemical obesogens, have been identified.  This article lists known obesogens.  One is called PFOA. It belongs to a large group of chemicals called PFAS.  As described in this NHS summary, PFAS have been used since the 1950’s.  They do not break down, but bioaccumulate, meaning they are building up in our bodies.

PFAS have been known to be toxic for decades, and some of the most dangerous have been banned.  PFOA/PFAS are used in waterproof clothing, stain repellant, and fire-fighting foam.  But more importantly, they are still allowed by the FDA for cookware and fast food packaging.  They are what make your eggs slide nicely out of the pan, and prevent grease from soaking into paper trays and burger wrap.

Think about this for a moment.  With every fast-food meal, a person absorbs PFAS, which potentially causes chemical changes in their body, promoting obesity.  Even more startling, the same thing could be happening every time they use a non-stick pan to cook food at home.

In this article, Consumer’s Reports found PFAS in paper packaging from every fast food outlet they visited.  This study found higher PFAS levels in the blood of people who ate in restaurants as well those who ate microwave popcorn.

In this recent study, dieters with highest levels of PFAS in their blood gained back the most weight.  This study also found the same thing: people with the highest PFAS levels gained the most weight, regardless of diet.

Could PFAS be a clue to why some people become obese and others do not?  Surely, this is an area that urgently needs more research.

Microbiome disruption - Antibacterial Soaps and other antimicrobials

The list of obesogens also includes the chemical triclosan.  Triclosan has been used since 1972 (note the proximity to 1978).  According to this summary, it was used widely in common antibacterial hand soap until it was banned in 2016.  But it is still allowed in toothpaste, mouthwash, hand sanitizer, and surgical soaps.  It is readily absorbed through the skin and has been shown to cause multiple health problems.

This study measured triclosan in urine and found a direct relationship to obesity.  The more triclosan, the higher the BMI.  The mechanism is complex but it is likely that, at the very least, triclosan increases BMI by disrupting the gut microflora.  Indeed, this article, confirmed that triclosan exposure can change gut bacteria.

Differences have been identified in the microbiomes of healthy vs. obese people.  (This article outlines differences in detail.)  Further, research has found that our gut bacteria can influence our behavior.  In other words, our gut bacteria may send signals to make us hungry or crave certain foods.  This article describes the way the gut-brain connection relates to obesity.  

How do the gut bacteria of obese people get disrupted?  Surely genetics and diet play a role.  But we also know that antibiotics, and other chemicals that kill microbes (antimicrobials) like triclosan can also upset the balance.

This article describes how gut bacteria can be altered by common food preservatives sodium benzoate, potassium sorbate and sodium nitrite.  This is particularly disturbing as carbonated soft drinks are usually preserved with potassium sorbate and sodium benzoate.  

We know that a poor diet, especially one lacking in fiber, can “starve” the gut microbiome.  But have we adequately considered factors in our environment, such as triclosan and food preservatives that could be actively killing off “good bacteria”?  More study is needed.


As we, as an industry, consider revisions to the Dietary Guidlines, the definition of “healthy” food, and possible front of pack nutrition claims, it is important to avoid unintended consequences. The effects of packaged food as well as restaurant and fast food should be considered.

We need to admit that even though consumers have heeded much of past dietary guidance, it has had no effect on obesity rates.

So it is important to consider the above three confounding factors that cannot be corrected by diet at all

Normalization is a delicate and heartbreaking social problem.  Obesoges are a terrifying environmental disaster that must be addressed through regulation.  And, as we learn more about the microbiome and how it supports and sustains the body, we need to protect it from the many types of antimicrobials in food and in the environment.

For the sake of struggling overweight people everywhere, I encourage the industry to think out of the box and consider these factors that have not been adequately researched.

About the author

Jan Matsuno is a Certified Food Scientist and founder of Yumbini healthy 6 minute beans and rice.  She has worked in the food industry for over 40 years and developed thousands of packaged food products.  She graduated from Oregon State University in 1979 so has had the dubious priviledge of watching the obesity epidemic unfold first hand.

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This Post Has One Comment

  1. Cathy Easton

    Excellent article Jan.

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