Effectiveness of energy-restricted diets with different protein:carbohydrate ratios: the relationship to insulin sensitivity

Abstract

Objective: Insulin sensitivity could determine the effectiveness of weight-loss diets with different protein:carbohydrate ratios. Our aim was to evaluate whether or not energy-restricted diets with different protein:carbohydrate ratios in obese individuals with (IR) or without (IS) insulin resistance could lead to differences in weight loss or insulin sensitivity. Design: Prospective, randomized, clinical intervention study. Thirty-six obese patients, allocated to the IR or IS group after a 75 g oral glucose tolerance test and calculation of the homeostasis model assessment of insulin resistance (HOMA) index, were assigned to follow an energy-restricted diet with either 40 % carbohydrate/30 % protein/30 % fat (diet A) or 55 % carbohydrate/15 % protein/30 % fat (diet B) and followed up to 16 weeks. Results: Twenty-one IR and fifteen IS patients were randomized to diet A or B. After 16 weeks, there was no difference in weight loss between diets A and B in each group. Glucose and insulin levels and HOMA were significantly reduced at 16 weeks, but no differences related to the type of diet were detected either in the IR or the IS group. Conclusions: Varying the macronutrient composition of a hypoenergetic diet, regarding the percentage protein:carbohydrate ratio, did not produce different weight loss or result in an improvement in insulin sensitivity in people with or without insulin resistance.

Dietary protein in weight management: a review proposing protein spread and change theories

“…Evidence weighs heavily toward studies showing anthropometric benefits of increased protein intake [2,11-44]. Those that did not support additional benefits still showed that higher protein was equally as good as an alternative diet [45-60]. …”

“…Additionally, protein intake spread between groups was often less than designed [45,46,48,57,61], a problem noted in a recent editorial [62]. …”

“…Thus, the traditional dogma of “energy in versus energy out” explaining weight and body compositional change is not entirely accurate. Another critique is that there are some studies in which greater protein is no more effective than control [45-60]. These studies do not find negative effects on body composition from higher protein, rather benefits are shown that are the same, but no greater than in controls [45-60].…”

“…Another critique is that there are some studies in which greater protein is no more effective than control [45-60]. These studies do not find negative effects on body composition from higher protein, rather benefits are shown that are the same, but no greater than in controls [45-60]. There has been little examination of why discrepancies in the protein and weight management literature exist.…”

“…Due primarily to limitations of dietary adherence in free-living adults, spread, or difference, in protein intake between groups during a study is often less than originally designed [45,46,57,61]. While this would seem an intuitive explanation for why some studies do not show greater body composition and anthropometric benefits of higher protein intakes it seems to have been largely overlooked until recently [62].…”