Ultra-Processed Foods and Obesity
Ultra-processed food and beverages have become a staple of the Western diet. The average American now obtains about 60% of their calories from ultra-processed products that are typically energy dense and nutrient poor with a high glycemic load (Figure 1). While the connection between overconsumption of these highly palatable products and obesity seems plausible, there is debate about whether industrial processing itself—independent of calories and macronutrient composition—contributes to adverse metabolic outcomes (e.g. excess fat accumulation, poor glycemic control).
To begin addressing this conundrum, researchers at the National Institutes of Health are conducting two controlled feeding studies of adults (aged 18-50 years) to assess how processed and unprocessed foods affect (1) daily food consumption and (2) metabolic health. Prepublication results from the first study comparing ad libitum energy intake on an ultra-processed diet versus an unprocessed diet for 14 days found that participants consumed more calories during the ultra-processed diet. Unsurprisingly, participants gained an average of about 2 pounds on the ultra-processed diet and lost about 2 pounds on the unprocessed diet. Results from the second study—in which the processed and unprocessed diets consumed are matched on calories, macronutrient composition, sugar, fiber, and sodium—are not yet available but will provide important insights on the metabolic effects of food processing.
Prior to these NIH studies, the link between diets rich in ultra-processed foods and ill health was supported only by large, observational analyses. These studies found correlations between:
Increased ultra-processed food consumption and excess weight. A cross-sectional analysisof anthropometric and dietary data from the National Health and Nutrition Examination Survey found that a diet with ≥74% of total energy from ultra-processed foods was associated with a 1.6 unit higher BMI, 4 cm greater waist circumference, and 62% higher odds of abdominal obesity (relative to a diet with ≤ 36.5 % of total energy from ultra-processed foods).
Increased ultra-processed food consumption and all-cause mortality risk. A prospective cohort study of middle-aged adults in France (NutriNet-Santé cohort) found a 14% increase in risk of all-cause mortality and a 12% increase in overall cancer risk for every 10% increase in the proportion of the participant’s diet composed of ultra-processed foods.
These data suggest that the high proportion of ultra-processed foods in the standard American diet contributes to our current health woes. Curbing consumption of ultra-processed foods, which have an estimated average sugar content 5 to 8 times higher than that of other minimally-processed and prepared foods, may indeed be an effective way to reduce added sugar intake.
However, reductions in ultra-processed foods will be a challenge. They are tasty, convenient, inexpensive, and have a long shelf-life. As the diversity of U.S. crops has declined over the past 30 years, the number of new packaged food and beverage products entering U.S. markets each year nearly doubledbetween 1998 and 2016 (11,853 vs. 21,435 products launched). The nation’s supply of vegetables would need to increase by an estimated 70% if all adults were to reduce ultra-processed food consumption and adopt diets consistent with USDA dietary guidelines. Limiting the availability and affordability of ultra-processed foods without ensuring universal access to unprocessed or minimally-processed foods at comparable cost would further disadvantage low-income populations for whom ultra-processed products tend to comprise a greater proportion of the overall diet. The studies of the impact of ultra-processed foods emphasize the need for a broad revision of our current agricultural and marketing policies to enable a reduction in disparities as well as the promotion of a healthful diet.