Written by Joyce Smith, BS. This study demonstrates how limiting consumption of ultra-processed foods may be an effective strategy for obesity prevention and treatment.
A 2018 Study by Monteiro et al 2018 1 describes ultraprocessed foods as “formulations mostly of cheap industrial sources of dietary energy and nutrients plus additives, using a series of processes” that contain minimal whole foods. The study also categorizes foods as a) minimally processes, b) processsed culinary ingredients, c) processed and d) underprocessed. There is a continuing debate that recommends the avoidance of ultra-processed foods 2,3 and, while they are inexpensive, they also offer long shelf-stability, provide important nutrients and are often conveniently ready to heat or eat. 4,5.
Hall and colleagues 6 designed the following study to examine whether processed food inherently leads to greater caloric intake than unprocessed food (where both diets are matched for carbohydrates, fats, protein, sugars, and other nutrients). Twenty participants from the National Institute of Health (NIH) Clinical Center were each randomized to alternately eat for two weeks each, an ultra-processed diet and an unprocessed diet. The two diets included meals that presented the same number of calories, energy density (number of calories per gram of food), macronutrients (e.g. fat, protein, carbohydrate), and total sugar, sodium, and fiber. Specifically, both diets contained approximate caloric breakdowns of 48% carbohydrate, 37% fat, and 14-16% protein and had similar energy density, sodium, and fiber content. However, due to the nature of ultra-processed foods, the ultra-processed diet had higher levels of sugar (added by the manufacturer) and fat, higher non-beverage energy density (calories per gram of food), and lower levels of insoluble fiber than the unprocessed diet. Participants were left at their discretion to eat as much or as little as they desired. All participants received three daily meals and had unlimited access to snacks.
Compared to those who ate unprocessed whole foods, participants who ate ultra-processed foods consumed an average of 2,979 daily calories, an average of 509 calories per day more than those on an unprocessed diet of 2,470 daily calories (p = 0.0001), reflecting an average weight gain of two pounds (p=0.009) over the two weeks. Conversely, consuming the unprocessed diet over two weeks resulted in an average weight loss of two pounds (p=0.007). The ultraprocessed diet provided significantly increased carbohydrates at breakfast, lunch and dinner, and significantly increased fats at breakfast and lunch. Protein intake was significantly lower only at lunch. There were no significant differences in calories expended by participants during sleeping or sedentary time or in physical activity.
The researchers suggest that the increase in calorie intake from the ultra-processed diet was driven by fats and carbohydrates – participants did not increase their protein intake, yet glucose tolerance and insulin sensitivity remained unchanged perhaps due to the impact of physical exercise. Also noteworthy was the fact that during the unprocessed diet, the appetite-suppressing hormone PYY increased compared to both the ultra-processed diet and baseline, while the hunger hormone ghrelin decreased compared to baseline. Interestingly, participants reported no significant differences in the pleasantness or familiarity of the two diets, suggesting that the increased caloric intake with the ultra-processed diet may have been due to an increased appetite and hunger.
The study data suggest that ultraprocessed food diets lead to weight gain and unprocessed diets support weight loss; however, reformulating ultraprocessed foods to eliminate their negative health effects may be difficult to implement. Until such time, low carbohydrate, low fat, and plant- and –animal –based diets should be encouraged. Hall believes that this two week study, supported by long-term observational research consistently linking ultra-processed diets to poor health outcomes, provides sufficient evidence to justify making the reduction of processed food intake a universal goal.
Study limitations include a failed to address whether cost and convenience influenced the participants’ choice of ultra-versus unprocessed foods. Also the study’s inpatient environment did not allow for generalization to free-living conditions.
Source: Hall, Kevin D., et al. “Ultra-processed diets cause excess calorie intake and weight gain: an inpatient randomized controlled trial of ad libitum food intake.” Cell metabolism 30.1 (2019): 67-77.
Posted April 12, 2021.
Joyce Smith, BS, is a degreed laboratory technologist. She received her bachelor of arts with a major in Chemistry and a minor in Biology from the University of Saskatchewan and her internship through the University of Saskatchewan College of Medicine and the Royal University Hospital in Saskatoon, Saskatchewan. She currently resides in Bloomingdale, IL.
References:
- Monteiro CA, Cannon G, Moubarac J-C, Levy RB, Louzada MLC, Jaime PC. The UN Decade of Nutrition, the NOVA food classification and the trouble with ultra-processing. Public health nutrition. 2018;21(1):5-17.
- Ministry of Health of Brazil. Dietary Guidelines for the Brazilian population. 2015.
- Moubarac J. Ultra-processed food and drink products in Latin America: Trends, impact on obesity, policy implications. Pan American Health Organization World Health Organization: Washington, DC, USA. 2015:1-58.
- Shewfelt RL. In Defense of Processed Food: It’s Not Nearly as Bad as You Think. Springer; 2016.
- Weaver CM, Dwyer J, Fulgoni VL, 3rd, et al. Processed foods: contributions to nutrition. Am J Clin Nutr. 2014;99(6):1525-1542.
- Hall KD, Ayuketah A, Brychta R, et al. Ultra-Processed Diets Cause Excess Calorie Intake and Weight Gain: An Inpatient Randomized Controlled Trial of Ad Libitum Food Intake. Cell Metab. 2019;30(1):67-77.e63.
