A professor at the School of Medicine and Health Sciences co-authored a medical review that urges researchers to develop guidelines demonstrating why eating fewer processed foods will prevent obesity.
Leigh Frame, a co-author of the article and program director for Integrative Medicine Programs, said her review shows that emulsifiers, or additives found in processed foods, correlate with higher rates of obesity. Obesity experts said no causal relationship between processed food and the rise of obesity has been proven, but Frame’s recommendations could influence food-related public policy and encourage consumers to make healthier food choices.
Frame said she referenced a study the National Institutes of Health conducted in July that indicates a strong correlation between a diet consisting of processed foods and obesity as a foundation for developing her recommendations.
She said the study found that markers of weight gain and chronic disease increased when participants ate processed foods with the same number of calories, fat, carbohydrates, protein and fiber as unprocessed foods – indicating that processed foods might increase the likelihood of weight gain.
“Chronic disease in later years is not predestined but heavily influenced by lifestyle and diet,” Frame said in an email. “Decreasing obesity and chronic disease in the U.S. will require limiting processed foods and increasing intake of whole vegetables, legumes, nuts, fruits and water.”
Frame said detailed recommendations to diet are needed to decrease the consumption of ultra-processed food – foods that have undergone a chemical operation – associated with weight gain, metabolic syndrome and chronic disease.
She said researchers need to “shift the conversation” from only discussing how “calories in versus calories out,” the yield of the number of calories eaten against the number lost through exercise or metabolism, affects weight gain and instead consider additional factors like hunger and fullness.
Frame said her article draws on recent research comparing the diets of “blue zones,” or areas like South America and the Mediterranean in which populations live much longer than average and contract low rates of chronic disease, to the typical diet of an American.
“Blue zone” inhabitants – whose diets primarily consist of foods high in fiber, minimally processed foods like nuts and rarely included meat – had far fewer chronic diseases, lower obesity rates and increased longevity than someone with the average American diet, according to the study.
Obesity experts said Frame’s recommendations stem from an emerging research focus on the relationship between diet and weight gain rather than assessing how the number of calories consumed or exercise level affect obesity rates.
Kevin Hall, a senior investigator at the National Institute of Diabetes, Digestive and Kidney Disease who co-wrote the study, said several recent studies – including his own – point to a positive association between processed food consumption and obesity. He said researchers are now focusing on the topic because people are increasingly consuming processed foods.
“There’s been a relatively recent focus on ultra-processed foods as being particularly important changes, which have clearly increased in the past several decades in the food supply,” Hall said.
He said publishing research that proves a causal relationship between obesity and eating processed foods could encourage food producers to adjust processing methods or influence policy makers to address overconsumption of ultra-processed meals.
“If we imagine that, in fact, ultra-processed foods as we showed do have a causal relationship to excess calorie intake and weight gain, one possibility might be if we could figure out what the mechanisms are, we could then reformulate ultra-processed foods to avoid instigating those mechanisms and avoid this problem,” Hall said.
Caroline Apovian, a professor of medicine and pediatrics at Boston University, said researchers need to prove that eating processed foods causes weight gain before policies can address the obesity epidemic. She said Frame’s medical review encourages a new conversation about healthy diets, but policies like taxing processed foods and soft drinks will likely not go into effect without research to substantiate a cause for obesity.
She added that lobbying for a new policy is expensive, so any proposal for a tax or ban on an item should be heavily supported with evidence explaining why the policy is necessary.
“So if we decide to ban processed food, then there’s no decrease in obesity rates, we just spent all this money banning a food that doesn’t cause obesity,” Apovian said.
Michael Schwartz, the co-director of the University of Washington’s Diabetes Institute, said lower-income neighborhoods have been projected to have higher rates of obesity because processed foods are typically more affordable than healthy foods. He said finding causation could shift how people view the value of their meals, encouraging them to seek out healthier choices.
“If you go and understand what the consequences of a specific type of diet might be, it helps to think about it from the point of view of what is, how is the bodyweight controlled and what might happen to the body weight control system when confronted with different types of diets,” Schwartz said.