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Ultra-Processed Diets Cause Excess Calorie Intake and Weight Gain
abstract
This abstract is available on the publisher's site.
Access this abstract now Full Text Available for ClinicalKey SubscribersWe investigated whether ultra-processed foods affect energy intake in 20 weight-stable adults, aged (mean ± SE) 31.2 ± 1.6 years and BMI = 27 ± 1.5 kg/m2. Subjects were admitted to the NIH Clinical Center and randomized to receive either ultra-processed or unprocessed diets for 2 weeks immediately followed by the alternate diet for 2 weeks. Meals were designed to be matched for presented calories, energy density, macronutrients, sugar, sodium, and fiber. Subjects were instructed to consume as much or as little as desired. Energy intake was greater during the ultra-processed diet (508 ± 106 kcal/day; p = 0.0001), with increased consumption of carbohydrate (280 ± 54 kcal/day; p < 0.0001) and fat (230 ± 53 kcal/day; p = 0.0004), but not protein (-2 ± 12 kcal/day; p = 0.85). Weight changes were highly correlated with energy intake (r = 0.8, p < 0.0001), with participants gaining 0.9 ± 0.3 kg (p = 0.009) during the ultra-processed diet and losing 0.9 ± 0.3 kg (p = 0.007) during the unprocessed diet. Limiting consumption of ultra-processed foods may be an effective strategy for obesity prevention and treatment.
Additional Info
Disclosure statements are available on the authors' profiles:
Ultra-Processed Diets Cause Excess Calorie Intake and Weight Gain: An Inpatient Randomized Controlled Trial of ad Libitum Food Intake
Cell Metab. 2019 May 16;[EPub Ahead of Print], KD Hall, A Ayuketah, R Brychta, H Cai, T Cassimatis, KY Chen, ST Chung, E Costa, A Courville, V Darcey, LA Fletcher, CG Forde, AM Gharib, J Guo, R Howard, PV Joseph, S McGehee, R Ouwerkerk, K Raisinger, I Rozga, M Stagliano, M Walter, PJ Walter, S Yang, M ZhouFrom MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
It is common sense that highly processed foods are not what we would want our patients to be consuming on a regular basis. What may be surprising is that they are now the most common source of calories for Americans and up to 90% of the added sugar consumed. What is more surprising is the lack of conclusive evidence on the harms of such diets as the authors point out:
“…no causal relationship between ultra-processed food consumption and human obesity has yet been established. In fact, there has never been a randomized controlled trial demonstrating any beneficial effects of reducing ultra-processed foods or deleterious effects of increasing ultra-processed foods in the diet.”
That is why NIH researcher Dr. Kevin Hall and colleagues set out to explore the effects of this diet which has important implications for the dietary advice we give our patients.
For clarity, the researchers wanted to compare diets which had foods that were unprocessed or minimally processed versus those that were ultra-processed. An example meal and snack for the two groups are listed below with a complete visual menu of the study meals created by researcher also available.
Intervention
For this month-long, well controlled experiment, the research recruited 20 weight-stable young adults (average age, 31 years; average BMI = 27) to reside in the NIH Clinical Center. For the first 2 weeks, the participants consumed either an ultra-processed diet or a calorically controlled unprocessed diet, with a crossover to the other group for the remaining 2 weeks. Importantly, during the trial, the participants were allowed to consume food as much or as often as desired (ad libitum) beyond the baseline diet. They were also asked to perform daily stationary bicycle exercise at a low intensity to avoid sedentary behavior. The research even measured the speed with which the foods were consumed.
Findings
Other key findings included:
Conclusions
The researchers concluded that limiting consumption of ultra-processed foods may be an effective strategy for obesity prevention and treatment.
Implications
This research study is the first to prospectively demonstrate in a well-controlled manner that ultra-processed diets promote weight gain. Although it could be argued (mostly by manufacturers of such foods) that the ultra-processed diet group consumed more and this could explain the weight gain—that is exactly the point and I am glad that the researchers created a design that captured the real world reality of “Betcha can’t eat just one!”
The fact is that these foods are engineered to create mindless overeating. They have the perfect fat-to-carb ratio, density, and mouth feel to make the consumer keep eating. The hormone changes and the increased speed of consumption point to previous research in animals, which has demonstrated that ultra-processed food cause immediate brain changes in reward centers that make them hard to avoid.1
Bottom-line
We have the strongest evidence to date that ultra-processed foods promote weight gain and hormonal changes associated with unhealthy eating behaviors. Keeping healthy dietary patterns, such as the Mediterranean diet, in mind, a more impactful starting point for many patients trying to lose weight or improve metabolic status might be discussing their intake and understanding of the impact of ultra-processed foods. Asking about intake of ultra-processed food such as the “Cs” (candy, chips, crackers, cookies, cakes, colas, and cold-cuts [processed meats]) and working toward healthy alternatives may be the best place to start. The visual menu from the study is also a nice tool to contrast these diets and provide examples of healthy alternatives.
Reference
A calorie is a calorie is a calorie; eat less and exercise more; any calorie can be part of a balanced diet. These are the mantras of the processed food industry. But are they real or fake news?
Hall and his NIH group attempted to answer this question with a 2-week crossover demand feeding study comparing the effects of real food (NOVA system class I, developed by Monteiro et al at the University of Sao Paolo) with ultra-processed food (NOVA system class IV). Hall locked up 20 subjects at the NIH Clinical Center, threw away the key, and fed them in random order and for 2 weeks at a time an ad lib processed food diet (more carbohydrate, less fiber) or an ad lib real food diet (less carbohydrate, more fiber). The two diets were matched for presented calories, sugar, fat, fiber, and macronutrients. Hall tracked food intake, body weight, energy expenditure, and baseline and glucose-stimulated hormonal parameters.
The ultra-processed food diet resulted both in weight gain and 508 calories per day greater intake (mostly carbohydrate) than the real food diet, which resulted in weight loss. The only things that distinguished the ingestion patterns were higher carbohydrate and less fiber in the ultra-processed diet. Finally, body weight changes correlated with changes in energy intake.
Bottom line: like other studies which preceded it (eg, the DIETFITS study), this study shows that real food works, and processed food doesn’t — take it to the bank. Real food resulted in fewer calories consumed, but we can’t infer that the effect was due to increased fiber (fewer calories absorbed); decreased energy density; reductions in carbohydrate; reductions in insulin and changes in leptin signaling; feeding the microbiome; and/or increased satiety.
And what about the food industry’s real versus fake news? Can we discern if, and which, macronutrients are the bad guys? What really reduced caloric intake? Unfortunately, this study was not designed or powered to assess whether certain macronutrients (like starch, fat, fructose) altered food intake apart from its caloric equivalent. Hall is a thermodynamics guy—and a calorie is always a calorie. So, don’t expect any other seminal answers out of this one.