Comparing appetite control and satiety effects for soya and meat-based high-protein diets

Alpro Foundation Supported Research

Prof. Alexandra Johnstone, University of Aberdeen, Rowett Institute of Nutrition and Health

One of the major challenges for preventing and treating obesity is hunger and appetite control. High protein diets (25-30% of total energy intake) have been shown to significantly increase satiety and reduce usual food intake. Therefore, higher protein intakes may be supportive for individuals trying to lose weight.

Most research in this field is based on dietary interventions with meat-based protein sources. We now know that diets with high intakes of meat are not sustainable for human or planetary health. Additionally, plant-based diets offer significant health benefits and are associated reduced incidence of chronic disease.

This Alpro Foundation supported study, lead by Professor Alexandra Johnstone, aimed to compare the effects of soya and meat protein food sources on appetite and satiety during weight loss.

Study overview

This was a cross-over study with 20 overweight or obese male participants who took part in a two-week clinical dietary intervention. Following a 3-day maintenance diet with medium protein intake (15% protein, 30% fat, 55% carbohydrate), participants consumed either a meat-based or a soya-based diet consisting of 30% protein, 30% fat and 40% carbohydrate for a period of 2-weeks. The high protein meat-based diet was based on chicken and beef whereas the high soya-protein diet consisted of soya drink, soya-based alternatives to yogurt and soya-based meat alternatives (burgers, mince, chicken-style filets). Individuals were provided with adequate energy to meet their measured resting metabolic rate.

Hunger, appetite and motivation to eat were measured hourly throughout the intervention using subjective visual analogue scales. Food diaries and body weight was assessed on a daily basis. During a final test meal, blood samples were collected to assess for biomarkers of satiety: plasma amino acid profile, ghrelin, glucagon like peptide 1 (GLP-1) and peptide YY (PYY).

Key findings

• At the end of the 2-week intervention:

  • Weight loss was similar for both the soya-based diet and the meat-based diet (average -2.41 vs -2.27 kg, respectively, P = 0.352).

  • Lean body mass preservation and fat percentage loss was also similar in both groups

• Throughout the intervention, no significant difference was observed for reported hunger, fullness and desire to eat between the soya and meat-based dietary groups

• Plasma amino acid profiles differed between baseline and the dietary groups, but this did not translate into changes in appetite

• Both groups significantly reduced LDL and HDL-cholesterol, triglycerides and blood glucose. Participants on the soya-based diet resulted in a significantly greater reduction in LDL cholesterol (p<0.05) and triglycerides (p<0.04)

Overall, both the soya-based and meat-based high protein diets resulted in similar weight loss and appetite control.

Conclusion

The researchers concluded that high-soya protein diets are as equally effective as meat-based high protein diets with regard to appetite control during weight loss interventions. Additionally, the cholesterol-lowering effect of soya protein was confirmed in this study. Thus, high protein plant-based diets provide a healthier alternative for individuals seeking weight management and appetite control benefits as they are not associated with the health risks often attributed to higher meat consumption. Moreover, these plant-based diets are more environmentally friendly.

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