Abstract
BackgroundWe previously reported that a weight-maintenance diet with a carbohydrate:protein:fat ratio of 30:30:40%, ingested for 5 weeks, improved blood glucose control in subjects with untreated type 2 diabetes. In this study we also determined that insulin and insulin-like growth factor-I (IGF-I) were increased. In this report we provide further information. Specifically, 24-hour total and individual amino acids, glucagon and cortisol data are provided. In addition, we determined whether these multiple effectors resulted in a positive nitrogen balance and an increase in fat-free mass. Insulin and IGF-I should stimulate protein accumulation. An increase in amino acids, particularly branched chain amino acids, should facilitate this, whereas glucagon and cortisol could have adverse effects in this regard.MethodsEight men with untreated type 2 diabetes were studied. A randomized crossover design was used. Data were obtained before and after 5 weeks on a control diet (55% carbohydrate:15% protein:30% fat) and on a 30% carbohydrate:30% protein:40% fat diet. Nitrogen balance and body composition were determined at the beginning and end of each dietary intervention.ResultsAs expected, the mean 24-hour total amino acid area response was higher after ingesting the 30:30:40 diet. However, the increase was only statistically significant for the branched chain amino acids, and phenylalanine and tyrosine. The 24-hour cortisol profile was unchanged. Glucagon was increased. Nitrogen balance was positive. Body weight was stable. Body composition and computed tomography data indicate no change in the fat-free mass.ConclusionThis high protein, low carbohydrate diet induced a metabolic milieu which strongly favors a positive protein balance, and a positive balance was present. However, an increase in lean (protein) mass was not documented. Whether such a diet in people with type 2 diabetes is useful in preventing or delaying the loss of total lean body mass and/or sarcopenia associated with aging remains to be determined.
Highlights
We previously reported that a weight-maintenance diet with a carbohydrate:protein:fat ratio of 30:30:40%, ingested for 5 weeks, improved blood glucose control in subjects with untreated type 2 diabetes
The circulating insulin-like growth factor-I (IGF-I) concentration is under control of growth hormone (GH) and circulates largely bound in a ternary complex of IGF-I, IGF-Binding Protein 3 (IGFBP-3) and a protein referred to as the Acid-Labile Subunit (ALS)
We previously evaluated the effect of a LoBAG30 diet on GH, IGF-I, IGFBP-3, IGF-Binding Protein-1 (IGFBP-1), and ghrelin [3]
Summary
We previously reported that a weight-maintenance diet with a carbohydrate:protein:fat ratio of 30:30:40%, ingested for 5 weeks, improved blood glucose control in subjects with untreated type 2 diabetes. In this study we determined that insulin and insulin-like growth factor-I (IGF-I) were increased. The insulin-like growth factor-I (IGF-I) concentration was increased regardless of the carbohydrate content in variations of the LoBAG diet. The circulating IGF-I concentration is under control of growth hormone (GH) and circulates largely bound in a ternary complex of IGF-I, IGF-Binding Protein 3 (IGFBP-3) and a protein referred to as the Acid-Labile Subunit (ALS). Free IGF-I may be partially regulated acutely by the concentration of IGF-Binding Protein-1 (IGFBP-1). We previously evaluated the effect of a LoBAG30 diet on GH, IGF-I, IGFBP-3, IGFBP-1, and ghrelin [3]. It may be involved in food intake regulation [7,8]
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