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What's Making Us Fat?

by David Tuller, DrPH  

Pat Crawford, DrPH, RD, senior director of research at the Nutrition Policy Institute at UC Berkeley, discusses the obesity epidemic, why nutrition research is so confusing, and the importance of federal nutrition guidelines.

Is the obesity epidemic really an “epidemic” or is that media hype?

Starting in the 1980s, national health surveys in the US have shown dramatic increases in weight and body-mass index among both children and adults. The astonishing magnitude of these increases and the fact that they have occurred over just a few decades, a relatively short period of time, and among varied population groups, are the marks of what we can truly call an epidemic. In the ‘80s and ‘90s, as obesity rates rapidly escalated, the US population became the fattest among the developed nations of the world.

Find out What's Behind the Obesity Epidemic.

How did that happen so quickly?

It wasn’t that millions of individuals suddenly lost their willpower or forgot how to choose the right foods. Instead, we began to see the overlapping effects of multiple changes in agriculture, technology, food production, and the nature of the labor force. For example, reliance on packaged foods and restaurant meals increased after women entered the work force in greater numbers. When people eat out, whether it’s due to larger portions or food preparation techniques, calorie consumption tends to increase, often by 200 or more calories per meal compared with home-cooked meals.

So what is the current situation?

A lot of attention has been focused on obesity prevention since the late ‘90s. The good news is that, during the last 15 years, the widespread increase in body mass index has slowed somewhat and in some groups, young children for example, it has even started to level off. The bad news is that the current high level of obesity and overweight, even if it stabilizes, has dramatic implications for the health and well-being of the population and for the national economy. Obesity is linked with higher rates of diabetes, cardiovascular disease, and other negative health outcomes, and an unhealthy population limits labor force participation and increases health care costs.

How about among children?

We have seen the same trends in weight among children and adolescents. Before 1980, about five percent of adolescents were obese. By 2012 the figure was almost 21 percent—over one in five of our youth. A significant number of today’s adolescents are suffering from obesity-related clinical manifestations of what used to be considered adult conditions, such as high blood pressure and type 2 diabetes. These are conditions that were basically non-existent in children 30 to 40 years ago. Today, national surveys are showing that nearly a quarter of adolescents have pre-diabetes or diabetes. This is a record-breaking statistic that is not acceptable for our children, for our economy or for the very future of our country.

We can take steps right now to protect children by making healthy food the most accessible. It has been shown that children will eat what’s there. One step that has been taken in the school setting is illustrated by this example: when high-fat, high-sugar snack foods and sodas were no longer sold at schools, students complained for a couple of weeks and then moved on to choosing healthier options that were made available.

There are many other opportunities to shift access from unhealthy to healthy foods in places where children live, learn, and play. Our bodies were programmed throughout evolutionary history to deal with food scarcity by seeking and consuming calorie-dense foods, with higher levels of sugars and fats. But in the context of our society’s current food system this adaptive evolutionary mechanism now makes children more vulnerable to the dangers of overconsumption. We must take steps to protect children from the this threat to their health, well being and longevity, as well as the threat that high chronic disease rates pose to our nation’s economy

How much is about nutritional intake, and how much about lack of physical activity?

Levels of physical activity are low in this country, and that’s an important health risk. However, we have not seen the dramatic change in physical activity levels since 1980 that we saw in the level of dietary intake. American men, on average, consumed 2080 calories a day in 1978, rising by almost 13 percent to 2347 calories in 1997, when the figure beganto stabilize. A similar increase happened with women. Those increases all by themselves explain the pounds gained in this country.

We’re constantly hearing news about foods or food ingredients being good or bad. How can we make sense of all these reports?

It is very confusing—we might hear caffeine can prevent cancer one day; on another day, we’re told it could increase heart disease. Further, the typical consumer doesn’t know the quality of the source of the “information,” even though the supposed results are in the news. Too often, individual studies of varying quality have their results reported in ways that are sensationalized or even misquoted, and reports often don’t make clear how the particular study fits into the broader context of related research. Sometimes cause and effect is implied when a study only described an association between two factors.

In contrast, our best evidence comes from the Dietary Guidelines process that we have in this country. Every five years, the US Health and Human Services Department and the Department of Agriculture put together a committee to evaluate research on food and nutrition. The guidelines they develop, based upon careful evaluation of the quality of the research and a preponderance of the evidence, are used to educate and inform the public. These Dietary Guidelines also provide the basis for federal nutrition policy. The federal food programs provide a safely net for vulnerable children and their families. Food programs such as school lunch depend on this synthesis of the scientific evidence to create healthy meal guidelines. Schools have recently started serving healthier foods as a result of changes in the school meal regulations, and this will help to reduce childhood obesity rates.

What is the latest from the Dietary Guidelines on fats and carbohydrates?

The guidelines on fats and carbohydrates haven’t changed significantly. We’ve known for years that there are better fats and worse fats. We have known that saturated fats are not good for one’s health, and the literature in support of that conclusion is strong. We’ve also known for years that trans fats are a health risk. The new federal dietary guidelines say that both saturated and trans fats should be reduced and replaced with healthier fats. With carbohydrates, we know that simple sugars and added sugars displace healthier foods. It is shocking that children consume about 40 percent of their calories from sugar and saturated fat. These are calories that promote obesity and, by replacing other foods, prevent children from meeting dietary requirements to promote health and prevent chronic disease risk.

The draft guidelines also note that eating a more plant-based diet would help the environment. How important is this?

Eating animal-based proteins has a much bigger impact on the environment than a plant-based diet. But due in large part to the impact of powerful industry forces, questions of whether we should be including environmental and sustainability concerns in our recommendations for a healthy diet are controversial. Currently there is a mismatch between the way we do agriculture and what the dietary guidelines say is a healthy diet. It is widely known that we do not produce sufficient fruits and vegetables for the population to be able to eat the recommended number of servings. This is apart from the widely recognized problem posed by the unavailability of adequate produce in many neighborhoods, especially those serving lower-income population groups.

What should consumers be paying attention to as the government reviews the draft 2015 dietary guidelines?

The dietary recommendations are based on the best science, and having strong and clear guidelines that promote healthy foods is the most effective way to reduce the risk of heart disease, diabetes, and cancer in the United States. Sadly, we have seen in the past how dietary recommendations have been weakened for political reasons—for example, the effort to classify ketchup as a vegetable.

Currently there is a discussion on whether the new school lunch standards are too hard for schools to implement, or whether children should be expected to eat such healthy foods. Yet reliable research shows that most schools are successfully implementing the healthier guidelines, and that children are eating the recommended foods. We must focus on helping the limited number of school districts that are struggling, rather than on lowering our nutrition standards that are an essential piece in efforts to improve the heath of our children.

As a society, if we are not vigilant in promoting the health of the children, then we are complicit. If we permit them to have constant access to inexpensive junk foods and beverages, we are part of the problem. Assuring healthy food access in all places where children live, learn, and play is akin to insisting on seatbelt protection and protection from smoking. Indeed the risk from an unhealthy diet is now the greatest contributor to the next generation’s risk of chronic disease.

This opinion does not necessarily reflect the views of the UC Berkeley School of Public Health or of the Editorial Board at

See also: Is Sugar Making Us Sick?