Responses in gut hormones and hunger to diets with either high protein or a mixture of protein plus free amino acids supplied under weight-loss conditions

What this study found

The high-protein diet improved appetite, but substituting part of the protein with free amino acids did not reproduce the same satiety effect. Composite hunger was 16% lower with HP than NP during the 5 h after breakfast and lunch (P < 0.01). NPAA produced the largest postprandial leucine and phenylalanine rises, yet hunger remained closer to NP than HP. Fasting and postprandial insulin, ghrelin, and peptide YY did not differ consistently across the weight-loss diets, and GIP showed only modest diet-related differences, supporting the authors' conclusion that free amino acids are unlikely to…

Study & population

Randomized crossover study in 18 overweight or obese adult men from North of Scotland.

Intervention

Participants completed three 10-day isoenergetic oral diet periods in a randomized crossover design: normal protein (NP; 15% of energy from protein), high protein (HP; 30% of energy from protein), and normal protein plus free amino acids (NPAA; 15% of energy from protein plus 15% of energy from free L-amino acids).

Key limitation

The sample was small and restricted to 18 overweight or obese men, which limits generalizability to women and broader populations.

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