Different mechanisms have been proposed to explain the relationship between ultra-processed foods and weight gain/obesity. Ultra-processed foods are energy-dense, meaning they contain a lot of calories in a very little amount of food. They are often high in saturated fat, trans fat, added sugar, and salt. Because the carbohydrate content is often simple/refined sugars, they contain no nutrient value but still cause blood sugar to spike. An alteration in the action of insulin, whose job is to allow sugar to enter cells, may occur, shuttling more glucose into fat cells. Some have proposed that the fat and sugar content of ultra-processed foods have a neurological impact similar to that of a reward system, which could lead to overconsumption and food-addiction behaviors. Some research, though, suggests there is another factor other than nutrient content that leads to obesity. Factors such as inviting packaging and ease of preparation may influence consumption of ultra-processed foods. Such factors might lead to mindless eating while multitasking that may mask hunger signals in the body. More research is needed in order to put all of the pieces together (Poti et al., 2017).
One study suggests that it is the amount of ultra-processed food that leads to weight gain. In this study conducted by the National Institutes of Health (NIH), twenty weight-stable adult subjects were randomized into two groups, one with an unprocessed diet and one with an ultra-processed diet. Each participant experienced both arms of the study at a two week interval and immediately started the opposite diet for the second two week interval. Across both groups, meals and snacks were matched for total calories, energy density, macronutrients, fiber, sugars, and sodium but differed in percentages of energy from either unprocessed or ultra-processed foods (i.e., the percentage of energy from ultra-processed food was 83.5% and 0% in the unprocessed diet, while in the unprocessed diet, the percentage energy from unprocessed food was 83.3% vs 6.4% in the ultra-processed group) (Hall et al., 2019). Participants were allowed to eat as little or as much as they wanted. Results showed that those eating an ultra-processed diet consumed ~500 calories/day more, mostly consisting of fat and carbohydrates. Those in the ultra-processed group gained approximately 2 lb more during those two weeks, and those in the unprocessed diet group lost approximately 2 lb during that time frame. There were no differences noted in palatability or appetite between the two groups. One interesting finding was that those in the ultra-processed diet group ate at a significantly faster rate, ~17 calories/minute greater. This suggests another possibility that the consistency of ultra-processed food may lead to an increased consumption rate and delayed satiety, resulting in increased intake (Hall et al., 2019).
Even though the study conducted by the NIH was conducted over a short period of time in a small group of subjects, with the relationship between ultra-processed foods and weight gain that was established, it is reasonable to suggest limiting ultra-processed food to achieve weight loss. When ultra-processed foods are consumed, it is important to be mindful of the rate of consumption. One strategy when it comes to consumption is to slow down and listen to your body. At UFit, we stress that nutrition is a big part of achieving health goals. Establishing a relationship with your body in that you give it what it needs and listen to its signals is part of the journey. Ultra-processed foods may not ever go away; it is all about moderation and factoring in certain foods into your dietary needs.