Obesity

Diet, Weight Management: Where Do Soyfoods Fit?

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With obesity rates rising across the globe, research has focused on questions about which dietary pattern is most conducive to losing weight and to maintaining weight loss.

One hypothesis is that diets high in protein-rich foods will spontaneously lead to a decrease in caloric intake and a loss in body weight because of the satiating quality of these foods.1 While in general evidence does support this hypothesis, compliance to high-protein diets can be problematic.2 There is also evidence that higher protein intake may help maintain muscle mass, an important issue for anyone who is losing weight, but particularly for older people.3 Soyfoods may play an important role in weight loss diets for this reason since they are higher in good quality protein than other plant foods.4,5

More recently research has aimed to determine whether diets that restrict either fats or carbohydrates have advantages for weight loss.6 Researchers from Stanford University assigned more than 600 obese men and women to either low-fat or low-carbohydrate diets for 12 months. The participants attended regular counseling sessions where they were instructed about which foods to consume or avoid. Regardless of which dietary pattern they were following, all participants were instructed to maximize vegetable intake; minimize intake of added sugars, refined flours, and trans fats; and focus on whole foods that were minimally processed, nutrient dense, and prepared at home whenever possible.

Average weight loss at the end of the year for both groups was about 13 pounds. Although the participants were not asked to reduce their calorie intake, people in both groups were consuming between 400 and 600 fewer calories per day throughout the study. Given the reported decrease in calorie intake, weight loss by the end of the year was surprisingly modest.

Although all of the participants were instructed to follow a diet that was either very low-fat or very low-carbohydrate, they were encouraged to liberalize their diet over time to reach a level of intake that they could sustain. Over the 12 months, diets among participants in both groups became less restrictive. It’s not clear at what point they would have stopped adding more fat or carbohydrates to their menus. Not surprisingly, caloric intake also slowly increased among both groups.

Further analysis of the findings showed that neither genetics nor individual responses to carbohydrates affected how well subjects did with either of these diets. The overall conclusions of the study were that adhering to a high-quality diet could translate to a reduction in calorie intake regardless of whether the diet is low in fats or carbohydrates.

Soyfoods can fit into either of these dietary approaches because of their versatility and nutrient profile. Most soyfoods, particularly tofu, are low in carbohydrates while soyfoods like textured vegetable protein and foods made from soy protein isolate can be low in fat.

References

  1. Astrup A. The satiating power of protein–a key to obesity prevention? Am J Clin Nutr. 2005;82(1):1-2.
  2. Leidy HJ, Clifton PM, Astrup A, et al. The role of protein in weight loss and maintenance. Am J Clin Nutr. 2015;1011320S-9S.
  3. Mitchell CJ, Milan AM, Mitchell SM, et al. The effects of dietary protein intake on appendicular lean mass and muscle function in elderly men: a 10-wk randomized controlled trial. Am J Clin Nutr. 2017;106(6):1375-83.
  4. Cope MB, Erdman JW, Jr., Allison DB. The potential role of soyfoods in weight and adiposity reduction: an evidence-based review. Obesity reviews: an official journal of the International Association for the Study of Obesity. 2008;9(3):219-35.
  5. Hughes GJ, Ryan DJ, Mukherjea R, et al. Protein digestibility-corrected amino acid scores (PDCAAS) for soy protein isolates and concentrate: Criteria for evaluation. J Agric Food Chem. 2011;59(23):12707-12.
  6. Gardner CD, Trepanowski JF, Del Gobbo LC, et al. Effect of low-fat vs low-carbohydrate diet on 12-month weight loss in overweight adults and the association with genotype pattern or insulin secretion: The DIETFITS randomized clinical trial. JAMA. 2018;319(7):667-79.
Dr. Mark Messina

Author Dr. Mark Messina

PhD in Nutrition, Executive Director, Soy Nutrition Institute. Expert in soyfoods and isoflavones.

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