Ultra-processed foods linked to overweight and obesity

Just last year we reported on a randomized, crossover study that required 20 adult men and women to live in the lab for 28 days. The participants consumed only the foods provided to them: for 14 days the participants were randomly assigned to either a highly-processed diet or a minimally-processed diet, then for an additional 14 days the participants switched diets.

The participants consuming an ultra-processed diet consumed more calories than those on a minimally-processed diet and gained about 2 pounds per week, while those on the minimally-processed diet lost about the same amount of weight per week. Both groups were initially presented with the appropriate number of calories for weight maintenance, but those consuming an ultra-processed diet weren't satisfied: they chose to consume more calories than those in the minimally-processed group.

A study recently published in the International Journal of Obesity (2020;44:2080-2091) takes a broader view: this research pools the results of 14 studies to examine if there might be a link between consumption of ultra-processed foods and the risk of being overweight or obese.

The authors identified observational studies published before November of 2019. To be included the studies had to measure the amount of ultra-processed food the participants consumed (with "ultra-processed" defined by an internationally-recognized food classification system, NOVA) and relate it to the participants' body weight as classified by clinically normal, clinically overweight, or clinically obese.

The included studies comprised almost 190,000 people participating in 14 studies published between 2014 and 2019. Ultra-processed food intake was measured using dietary questionnaires in 5 studies, 6 studies used 24-hour dietary recalls, 1 looked at grocery store receipts, and the rest relied on evaluating the foods already purchased and in the home. One study focused on pregnant women alone; all other studies included both women and men.

Six of the studies were eligible to be used in the authors' meta-analysis comparing those who consumed the most ultra-processed foods with those who consumed the least. That ultra-processed food consumption increased the risk of obesity - not just overweight - by 26%, even though the included studies largely took into account Body Mass Index and caloric intake.

What this means for you

This shouldn't be much of a surprise: ultra-processed foods tend to be calorie-dense, high in refined carbohydrates, and low in both fiber and protein - two elements that help make foods satisfying. Instead, cook your own meals from scratch - it's cheaper than you think - and make extra so you have leftovers for lunches or dinners later in the week.

First posted: December 2, 2020