Dairy protein, calcium and body weight —the need for a mechanism

The effects of calcium channel blocker benidipine and calmodulin antagonist W7 on GDP-binding capacity of brown adipose tissue in mice

It has been suggested that increased dietary calcium intake can attenuate obesity. Calcium antagonists, such as benidipine, also have been shown to have an anti-obesity effect. However, the mechanism for calcium-related anti-obesity effect has not yet been established. A defective brown adipose tissue thermogenesis has been shown in obese rodents. This study was designed to examine the direct effects of calcium channel blocker benidipine and calmodulin antagonist W7 administration on the adaptive thermogenesis in brown adipose tissue taken from the genetically obese mice and their lean controls. The GDP binding to brown-fat cell mitochondria was used as a brown adipose tissue thermogenic index. The results show that benidipine treatment had no marked effect on brown-fat cell GDP-binding capacities in both obese and lean mice. However, GDP-binding capacities were significantly reduced in both obese and lean mice after the W7 administration. The results of this study support the previous finding that benidipine did not have direct thermogenic effect on brown adipose tissue and suggest that the change in intracellular calmodulin availability might contribute to the adaptive thermogenesis in brown adipose tissue.

Calcium supplementation does not alter lipid oxidation or lipolysis in overweight/obese women

Based on cell culture and studies in mice, increased dietary calcium appears to stimulate lipolysis and could possibly reduce body adiposity through hormonal influences on adipocyte calcium uptake. In this study, we investigated the effects of 1,500 mg supplemental calcium daily for 3 months on hormones regulating calcium and energy metabolism and rates of lipid oxidation and lipolysis in overweight women. Fifteen overweight (BMI > 25 kg/m(2)) premenopausal women were supplemented with 1,500 mg of calcium, as CaCO(3), per day for 3 months while maintaining their usual diets and activity levels. Baseline and endpoint measurements were obtained after the subjects consumed a standardized 25% fat diet for 4 days. Lipid oxidation was measured by indirect calorimetry, lipolysis by infusion of deuterated glycerol, and body fat by dual-energy X-ray absorptiometry. Urinary calcium, circulating levels of hormones involved in energy and lipid metabolism (insulin, leptin, and adiponectin) or calcium metabolism (25(OH)D, 1,25(OH)(2)D), and parathyroid hormone (PTH)) were also measured. Urinary levels of calcium (P = 0.005) increased and 1,25(OH)(2)D declined (P = 0.03). However other parameters, including body weight, body fat, PTH, insulin, leptin, adiponectin, 25(OH)D, as well as rates of lipid oxidation and lipolysis were not altered by calcium supplementation. Calcium supplementation for 3 months increased urinary calcium excretion, decreased circulating levels of 1,25(OH)(2)-D, but had no effect on rates of lipid oxidation or lipolysis, in these overweight women.

High-calcium diet with whey protein attenuates body-weight gain in high-fat-fed C57Bl/6J mice

An inverse relationship between Ca intake and BMI has been found in several studies. It has been suggested that Ca affects adipocyte metabolism via suppressing 1,25-dihydroxycholecalciferol (1,25(OH)2-D3) and decreases fat absorption. We studied the effect of Ca and milk proteins (whey and casein) on body weight in C57Bl/6J mice. Male mice, age 9 weeks, were divided into three groups (ten mice per group) receiving modified high-fat (60% of energy) diets. Two groups received a high-Ca diet (1.8% calcium carbonate (CaCO3)), with casein or whey protein (18% of energy), and one group received a low-Ca diet (0.4% CaCO3) with casein for 21 weeks. Food intake was measured daily and body weight twice per week. Body fat content (by dual-energy X-ray absorptiometry) of all mice and faecal Ca and fat excretion of seven mice/group were measured twice during the study. Final body weight (44.1 (SEM 1.1) g) and body fat content (41.6 (SEM 0.6) %) were significantly lower (P < 0.05) in the high-Ca whey group than in the low-Ca casein group (48.1 (SEM 0.8) g and 44.9 (SEM 0.8) %). Body weight and body fat content of the high-Ca casein group did not differ significantly from the low-Ca casein group even though serum 1,25(OH)2-D3 levels were significantly lower (P < 0.001) in both high-Ca groups than in the low-Ca casein group. Thus changes in serum 1,25(OH)2-D3 do not seem to affect body weight in this animal model. There was a significant difference in fat excretion between the high-Ca whey and low-Ca casein groups (3.9 (SEM 0.9) % in the high-Ca whey v. 1.4 (SEM 0.2) % in the low-Ca casein group; P < 0.05), which may partly explain the effect on body weight.

Dietary strategies for the prevention of obesity

The rising tide of obesity has led to a resurgence of interest in dietary strategies to prevent excess weight gain. Data from controlled intervention studies is sparse, but nonetheless evidence from other diverse sources has identified a number of specific dietary factors and aspects of eating behaviour that either promote or protect against obesity. The present paper reviews the evidence in relation to energy density, the macronutrient composition of the diet, including the nature of carbohydrate foods and sugar-rich drinks, portion size and snacking habits. It concludes that there is now sufficient evidence to develop clear dietary guidelines to prevent weight gain that are largely consistent with those for the prevention of CVD and cancer. However, coordinated action across multiple stakeholders is also required if these guidelines are to be translated into sustained changes in eating habits.