Patient freedom to choose a weight loss diet in the treatment of overweight and obesity: a randomized dietary intervention in type 2 diabetes and pre-diabetes.

BACKGROUND: Offering the overweight or obese patient the option of choosing from a selection of weight loss diets has not been investigated in type 2 diabetes. The aim of the study was to investigate if the option to choose from, and interchange between a selection of diets ("Choice"), as opposed to being prescribed one set diet ("No Choice"), improves drop out rates and leads to improved weight loss and cardio-metabolic outcomes. METHODS: The study was a 12 month, randomized parallel intervention. A total of 144 volunteers with type 2 diabetes or pre-diabetes and a BMI >27 were randomized to "No Choice" or "Choice". Those in the No Choice group were placed on a set weight loss diet (CSIRO) with no change permitted. Those in the Choice group could choose from, and interchange between, the CSIRO, South Beach or Mediterranean diets. RESULTS: There were no differences in attrition rates or weight loss between the "Choice" and "No Choice". In a secondary analysis of the intention-to-treat weight loss data with last measured weight carried forward gave a highly significant diet group by time by gender interaction (p = 0.002) with men doing better in the No Choice group overall (maximum difference "No Choice "-2.9 ± 4.6 kg vs. "Choice"-6.2 kg ± 5.3 kg at 6 months) and women doing better in the Choice group overall (maximum difference Choice -3.1 ± 3.7 kg vs. "No Choice" -2.0 kg ± 2.6 kg at 6 months). CONCLUSIONS: Men prefer direction in their weight loss advice and do less well with choice. A gender-specific approach is recommended when prescribing weight loss diets. TRIAL REGISTRATION: anzctr.org.au ACTRN12612000310864.

Validation of a dual in vivo-in vitro assay for predicting the digestibility of nutrients in humans.

BACKGROUND: The validation of a dual in vivo-in vitro digestibility assay ('dual digestibility assay') for separately predicting the upper-tract, hindgut and total tract digestibility of nutrients in humans, as estimated using organic matter digestibility (OMD), is described. Human upper-tract OMD was predicted using an animal (rat) model with digesta from the terminal ileum collected from rats fed one of four complete human diets (wheat bran diet, pectin diet, mixed low-fibre diet, mixed high-fibre diet). Large intestinal OMD was predicted using an in vitro hindgut fermentation assay employing a human faecal inoculum and with the rat ileal digesta as the substrate. RESULTS: A comparison of total tract OMD of the four diets from a human balance study (OMDhuman ) with that predicted using the dual digestibility assay (OMDdual ) showed no significant differences (P > 0.05). OMDhuman and OMDdual were highly correlated (r = 0.953, P = 0.047). CONCLUSION: The dual digestibility assay accurately predicts the uptake of dietary nutrients (as grams of organic matter) in humans over the total tract. The assay is able to separately quantify the digestibility of nutrients in the upper and lower digestive tracts. The validation of the dual digestibility assay needs to be extended to a wider range of human diets.

Effect of beetroot juice on lowering blood pressure in free-living, disease-free adults: a randomized, placebo-controlled trial.

BACKGROUND: The consumption of beetroot juice on a low nitrate diet may lower blood pressure (BP) and therefore reduce the risk of cardiovascular events. However, it is unknown if its inclusion as part of a normal diet has a similar effect on BP. The aim of the study was to conduct a randomized controlled trial with free-living adults to investigate if consuming beetroot juice in addition to a normal diet produces a measureable reduction in BP. METHOD: Fifteen women and fifteen men participated in a double-blind, randomized, placebo-controlled, crossover study. Volunteers were randomized to receive 500 g of beetroot and apple juice (BJ) or a placebo juice (PL). Volunteers had BP measured at baseline and at least hourly for 24-h following juice consumption using an ambulatory blood pressure monitor (ABPM). Volunteers remained at the clinic for 1-h before resuming normal non-strenuous daily activities. The identical procedure was repeated 2-wk later with the drink (BJ or PL) not consumed on the first visit. RESULTS: Overall, there was a trend (P=0.064) to lower systolic blood pressure (SBP) at 6-h after drinking BJ relative to PL. Analysis in men only (n=13) after adjustment for baseline differences demonstrated a significant (P<0.05) reduction in SBP of 4 - 5 mmHg at 6-h after drinking BJ. CONCLUSIONS: Beetroot juice will lower BP in men when consumed as part of a normal diet in free-living healthy adults. TRIAL REGISTRATION: anzctr.org.au ACTRN12612000445875.

Predicted apparent digestion of energy-yielding nutrients differs between the upper and lower digestive tracts in rats and humans.

The apparent digestibility of energy-yielding nutrients (carbohydrate, protein, and fat) was predicted in the human upper digestive tract and large bowel separately for 4 diverse diets containing either a single dietary fiber source [wheat bran and pectin (PE) diets] or mixed fiber sources [low-fiber (LF) and high-fiber (HF) diets). A human balance study was undertaken to determine fecal energy and nutrient excretion and a rat model was used to predict human ileal energy and nutrient excretion. Total tract energy digestibility ranged from 92 (HF diet) to 96% (PE diet and LF diet), while at the ileal level it ranged from 79 to 86% for the HF diet to the LF diet. The predicted upper-tract digestion of starch, sugars, and fat was high, with ileal digestibilities exceeding 90% for all diets. Nonstarch polysaccharides were poorly digested in the upper tract for all diets except in the PE diet. The daily quantity of protein excreted at the ileal level was between 2 (HF diet) and 5 (PE diet) times higher than that at the fecal level. The large differences between fecal and ileal nutrient loss highlight that fecal digestibility data alone provide incomplete information on nutrient loss. There is a need to be able to routinely determine the uptake of energy in the upper and lower digestive tracts separately.

Optimisation of inoculum concentration and incubation duration for an in vitro hindgut dry matter digestibility assay.

The aim was to optimise inoculum concentration and incubation duration for a published in vitro hindgut digestibility assay using ileal digesta (sampled from the chicken or rat) pertaining to a mixed human diet as the substrate. The study also sought to investigate the digestibility of the inoculum itself and the importance of correcting for this in the in vitro hindgut digestion assay. For two assays, hindgut dry matter digestibility (DMD) generally increased with inoculum concentration. A sharp increase in DMD observed at high inoculum concentrations may have been related to problems with filtering the inoculum. An inoculum concentration of 160 g/L was considered optimal based on close agreement of observed values with previously published in vivo hindgut dry matter digestibility for similar diets. One of the methods was chosen for optimisation of the duration of incubation. Ileal substrate organic matter digestibility (OMD) increased with increasing time of incubation for all diets. An incubation duration of 18 h using a mean inoculum digestibility value for calculation purposes was considered optimal based on observed in vivo hindgut DMD values in humans, but there was little difference in estimated in vitro hindgut DMD between 18 and 24h incubation durations. Although considerably lower than the OM digestibility of the substrate (no less than 51% after 48 h), the OM digestibility of the inoculum (13% after 48 h) itself was of significance in calculating estimated digestibility. The optimised assay gave realistic hindgut OMD values ranging from 55% to 79% (Wheat Bran Diet and Pectin Diet, respectively) using an 18-h incubation duration.