Abstract
High protein diets and low glycemic index (GI) diets have been associated with improved diet quality. We compared the changes in nutrient intakes of individuals at high risk of developing type-2 diabetes over 3 y who followed either a higher protein-lower GI diet (HPLG) or a conventional moderate protein-moderate GI diet (MPMG). This post hoc analysis included 161 participants with overweight and pre-diabetes from the Australian cohort of the PREVIEW study (clinical trial registered in https://www.clinicaltrials.gov/ct2/show/NCT01777893?term=NCT01777893&draw=2&rank=1) who were randomly assigned to a HPLG diet (25% energy from protein, dietary GI ≤ 50, n = 85) or a MPMG diet (15% energy from protein, dietary GI ≥ 56, n = 76). Food records were collected at 0-mo (baseline) and at 6-, 12-, 24-, and 36-mo (dietary intervention period). Linear mixed models were used to compare the differences in total energy, macro- and micronutrients, dietary GI, glycemic load (GL) and body weight between the two diet groups at the 4 dietary intervention time points. At 3 y, 74% participants from the HPLG diet and 74% participants from the MPMG diet completed the trial. The HPLG group showed significantly higher protein intake and lower dietary GI and GL than the MPMG group (group fixed effect P < 0.001 for all three parameters). By 6-, 12-, 24-, and 36-mo there was a 3.0, 2.7, 2.2, and 1.4% point difference in protein intake and 6.2, 4.1, 4.8, and 3.9 GI unit difference between the groups. The intake of energy and saturated fat decreased (mostly in the first 6-mo), while the intake of dietary fiber increased (from mo-0 to mo-12 only) in both diets, with no significant differences between the diets. The dietary intakes of zinc (group fixed effect P = 0.05), selenium (P = 0.01), niacin (P = 0.01), vitamin B12 (P = 0.01) and dietary cholesterol (group by time fixed effect P = 0.001) were higher in the HPLG group than in the MPMG group. Despite both diets being designed to be nutritionally complete, a HPLG diet was found to be more nutritious in relation to some micronutrients, but not cholesterol, than a MPMG diet.
Highlights
Weight gain resulting in overweight (BMI ≥ 25–30 kg/m2) and obesity (BMI > 30 kg/m2) is a major contributor to the risk of developing type 2 diabetes (T2D) [1]
To the best of our knowledge, this is the first study comparing the nutrient density of a healthy higher protein-lower GI diet (HPLG) diet and of a healthy moderate protein-moderate GI diet (MPMG) diet prescribed for a 3-y period
With comparable reductions in energy intake between the two groups during the intervention, individuals following the HPLG diet consumed higher intakes of some micronutrients than those assigned to the MPMG diet
Summary
Weight gain resulting in overweight (BMI ≥ 25–30 kg/m2) and obesity (BMI > 30 kg/m2) is a major contributor to the risk of developing type 2 diabetes (T2D) [1]. Based on the results from the DiOGenes (Diet, Obesity and Genes) study [10], which showed improved weight loss maintenance over 4-mo by following a HPLG diet, the PREVIEW trial hypothesized that a HPLG dietary intervention would be more effective than a conventional MPMG intervention in preventing T2D [9]. Both diets with a low dietary GI and/or low glycemic load (GL), and diets with higher percentage of total energy from protein have been previously found to be protective against T2D [6, 11]. Statistical significance was determined by an α level of 0.05
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