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Ultra-Processed Food and Weight

8/6/2019 1:56:20 PM
processed foodsThe rise in obesity has paralleled the increased industrialization of processed foods. Ultra-processed foods have become common worldwide and make up the majority of calories consumed in the United States. Ultra-processed foods are typically high in calories, salt, sugar, and fat but low in essential nutrients. Some are engineered to disrupt normal appetite control.

Researchers examine obesity-appetite-processed foods connection

Despite the associations between obesity and processed foods, no causal relationship between these two variables has been established. To explore a causal connection, researchers at the National Institutes of Health (NIH) conducted a randomized controlled trial.

The trial was conducted at the Metabolic Clinical Research Unit at the NIH Clinical Center. Ten men and 10 women (aged 31.2 ± 1. 6 years) with stable weight (BMI = 27 ± 1.5 kg/m2) resided in the research unit for 28 consecutive days. Participants were randomly assigned to the ultra-processed or unprocessed diet for 2 weeks and then the other diet for the second 2 weeks. All participants performed daily low-intensity cycle exercise in three 20-minute bouts.  

Consuming processed foods means more calories, faster consumption

The diets were matched for total calories, energy density, macronutrients, fiber, sugar, and sodium. However, the ultra-processed diet provided significantly higher ratios of added sugar to total sugar, insoluble fiber to total fiber, and saturated to total fat. The ratio of omega-6 to omega-3 fatty acids was also significantly different between the ultra-processed and unprocessed diets (11:1 vs. 5:1).
When presented with the same total calories per day, energy intake was ~500 kcal greater during the ultra-processed diet (p=.0001). The increased energy intake resulted from consuming more carbohydrate and fat but not protein. The speed of eating meals was significantly faster during the ultra-processed diet than the unprocessed diet.

Different diets, different effects on weight 

Participants gained 0.9 ± 0.3 kg during the ultra-processed diet and lost 0.9 ± 0.3 kg during the unprocessed diet. These differences in weight change were highly correlated with the energy intake differences between the diets. Also, body fat mass increased by 0.4 ± 0.1 kg during the ultra-processed diet and decreased by 0.3 ± 0.1 kg during the unprocessed diet.
Results also showed that the appetite-suppressing hormone PYY increased during the unprocessed diet, and the hunger hormone ghrelin decreased. The unprocessed diet led to decreases in adiponectin, total cholesterol, hsCRP, and total T3 but increases in free T4 and free fatty acids. There were no significant differences between the diets in HOMA-IR or the oral glucose tolerance test at the end of each diet period.  
This 28-day randomized controlled trial is the first study of its kind to suggest that eating a diet high in ultra-processed foods may increase energy intake and lead to weight gain.

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;

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