Prescription of energy-restricted diets with higher and lower pork protein content achieves weight loss and improved glycaemic control in adults with type 2 diabetes

Energy-restricted, high-protein diets have shown to be effective for enhancing weight loss and improving glycaemic control in type 2 diabetes (T2DM) (Dong et al. 2013). Regular pork consumption has also been shown to improve weight loss and body composition both without energy-restriction (Murphy et al. 2012) and during energy restriction (Wycherley et al. 2010), but there is little data available on whether benefits are maintained during weight maintenance following initial weight loss. The aim of this study was to compare the effects of a higher pork protein content (HPP) and a lower pork protein (LPP) diet on weight loss and glycaemic control (measured by glycosylated haemoglobin [HbA1c %]) in overweight and obese adults with T2DM during weight loss and subsequent weight maintenance. It was hypothesised that an energy-restricted HPP diet would result in greater reductions in weight and HbA1c than the LPP diet during weight loss, and these improvements would be sustained during subsequent weight maintenance.

Sixty-one overweight and obese adults (aged 37–67 years; body mass index [BMI] 34.3 ± 0.6 kg/m² (mean ± SEM) with moderately controlled T2DM (HbA1c 8.1 ± 0.2%) were randomised to one of two hypocaloric diets: HPP diet (38% carbohydrate, 30% protein, 29% fat) or a LPP diet (53%:21%:23%) for 12 weeks, after which energy was adjusted to maintain a stable weight for a further 12 weeks while preserving the allocated macronutrient profile. Fresh, lean pork consisting of fillet steaks, stir-fry strips or diced pork, was prescribed for four times per week throughout the study (HPP 200-250 g/serves; LPP 100–150 g/serves). At baseline, participants completed a Food Frequency Questionnaire (FFQ) to assess habitual pork intake (frequency and portion size) over the previous 12 months. Daily semi-quantitative food checklists were completed throughout the study to capture dietary compliance. Dietary advice, meal planning and recipe ideas were provided every 2 weeks. Participants performed regular aerobic exercise throughout. Outcomes were measured at baseline and the end of each diet phase (Weeks 0, 12 and 24). Data were analysed using a linear mixed effects model utilising all data collected regardless of study completion (IBM SPSS, Version 21.0; USA).

Forty-four participants completed the study (HPP n = 23, LPP n = 21). Habitual intakes indicated the participants were infrequent pork consumers prior to entering the study (median, range: HPP 49.0 g/week, 0 to 305 g/week, LPP 52.5 g/week, 0 to 613 g/week, P = 0.77). During the weight loss phase, average pork consumption was 720 ± 29 g/week for the HPP diet and 384 ± 31 g/week for the LPP diet (P < 0.001). This indicates a 90 ± 3% and 94 ± 3% compliance with the prescribed pork intake for the diet groups respectively. There was a small decrease in compliance during the weight maintenance phase but this did not reach significance for time (P = 0.06) or between diet groups (P = 0.71). At the end of the 12-week weight loss phase, both groups showed reductions (P < 0.001) in weight (HPP –8.0 ± 0.8 kg; LPP –7.6 ± 0.8 kg) and improvements in HbA1c (HPP –1.5 ± 0.2%; LPP –1.3 ± 0.2%), with no differences between diets (P > 0.05). Following the 12-week weight maintenance phase, weight and HbA1c remained stable (P > 0.05).

Both diets achieved substantial weight loss and improvements in glycaemic control following energy-restriction that was sustained during weight maintenance. These data suggest lean pork can be included as part of a weight loss program for overweight and obese individuals with T2DM to achieve benefits for glycaemic control.