Moderate dietary weight loss reduces myocardial steatosis in obese and overweight women.

BACKGROUND: Excessive myocardial triglyceride (MTG) content in obesity and type 2 diabetes is associated with impaired cardiac function. Previous studies suggest that MTG could be mobilized through lifestyle interventions. We assessed influences of moderate dietary weight loss in non diabetic obese and overweight women on MTG content and cardiac function. METHODS: We selected a subgroup of 38 women from the B-SMART study population. The B-SMART study compared weight loss and associated metabolic and cardiovascular markers with reduced-carbohydrate and reduced-fat hypocaloric diets. Selected subjects had completed a cardiac magnetic resonance (MR) scan including imaging and proton spectroscopy to assess cardiac structure and function as well as MTG content. RESULTS: An average weight reduction of 5.4 ± 4.3 kg at six months was associated with a relative decrease of MTG of 25% (from 0.72 ± 0.29% at baseline to 0.54 ± 0.23% at follow-up, p<0.001). The response was similar with carbohydrate and fat restriction. Diastolic function expressed as ratio of peak filling rate in E- and A-Phase (PFRE/PFRA) was unchanged. Reductions of left atrial size (from 21.9 ± 4.0 cm(2) to 20.0 ± 3.7 cm(2), p=0.002), the normalized ratio of PFRE and early diastolic lengthening velocity PLV (from 8.2 ± 2.6 to 7.5 ± 2.5, p<0.001) and fat free mass (from 55.1 ± 6.9 kg to 52.7 ± 6.5 kg, p=0.007) reflected altered cardiac volume loading after diet, but did not correlate to MTG content. CONCLUSIONS: Moderate dietary weight loss significantly reduced MTG content in women with uncomplicated overweight or obesity. Macronutrient composition of the diet did not significantly affect the extent of MTG reduction.

Left ventricular mass and function with reduced-fat or reduced-carbohydrate hypocaloric diets in overweight and obese subjects.

In animals, carbohydrate and fat composition during dietary interventions influenced cardiac metabolism, structure, and function. Because reduced-carbohydrate and reduced-fat hypocaloric diets are commonly used in the treatment of obesity, we investigated whether these interventions differentially affect left ventricular mass, cardiac function, and blood pressure. We randomized 170 overweight and obese subjects (body mass index, 32.9±4.4; range, 26.5-45.4 kg/m(2)) to 6-month hypocaloric diets with either reduced carbohydrate intake or reduced fat intake. We obtained cardiac MRI and ambulatory blood pressure recordings over 24 hours before and after 6 months. Ninety subjects completing the intervention period had a full cardiac MRI data set. Subjects lost 7.3±4.0 kg (7.9±3.8%) with reduced-carbohydrate diet and 6.2±4.2 kg (6.7±4.4%) with reduced-fat diet (P<0.001 within each group; P=not significant between interventions). Caloric restriction led to similar significant decreases in left ventricular mass with low-carbohydrate diets (5.4±5.4 g) or low-fat diets (5.2±4.8 g; P<0.001 within each group; P=not significant between interventions). Systolic and diastolic left ventricular function did not change with either diet. The 24-hour systolic blood pressure decreased similarly with both interventions. Body weight change (ß=0.33; P=0.02) and percentage of ingested n-3 polyunsaturated fatty acids (ß=-0.27; P=0.03) predicted changes in left ventricular mass. In conclusion, weight loss induced by reduced-fat diets or reduced-carbohydrate diets similarly improved left ventricular mass in overweight and obese subjects over a 6-month period. However, n-3 polyunsaturated fatty acid ingestion may have an independent beneficial effect on left ventricular mass.

Myocardial steatosis, cardiac remodelling and fitness in insulin-sensitive and insulin-resistant obese women.

BACKGROUND: Obesity predisposes to heart failure and premature cardiovascular death, particularly in sedentary women. In animal models and in men with type 2 diabetes mellitus, impaired cardiac function is associated with myocardial triglyceride (MTG) accumulation. Lipotoxic injury from altered myocardial metabolism may be causative. Whether such association also exists in obese, non-diabetic women is unknown. OBJECTIVE: To explore the relation between MTG content, cardiac remodelling and cardiorespiratory fitness in obese, insulin-sensitive and insulin-resistant non-diabetic women. DESIGN: Cross-sectional investigation. SETTING: Academic clinical research centre. PATIENTS: 65 Overweight/obese and sedentary, but otherwise healthy women (body mass index 33±4 kg/m(2); age 45±10 years). INTERVENTIONS: None. MAIN OUTCOME MEASURES: Cardiac structure and function measured by cardiovascular magnetic resonance imaging and MTG content of the interventricular septum by (1)H MR spectroscopy. Additional outcomes were cardiopulmonary fitness and insulin sensitivity during oral glucose tolerance testing. RESULTS: Insulin resistance (composite insulin sensitivity index (C-ISI) <4.6) was present in 29 women. MTG content was higher (0.83±0.30 vs 0.61±0.23, p=0.002) and left ventricular diastolic (p<0.01), but not systolic function was reduced in women with insulin resistance compared with insulin-sensitive women. The remodelling index defined as left ventricular mass divided by end-diastolic volume was increased in women with impaired glucose tolerance (p=0.006). Furthermore, cardiopulmonary fitness was equal in both groups, but was inversely correlated with MTG (r=-0.28, p=0.02). CONCLUSIONS: In overweight and obese women, insulin resistance is associated with increased MTG content, cardiac remodelling and reduced diastolic function. CLINICAL TRIAL REGISTRATION: ClinicalTrials.gov NCT00956566.

Randomized comparison of reduced fat and reduced carbohydrate hypocaloric diets on intrahepatic fat in overweight and obese human subjects.

UNLABELLED: Obesity-related hepatic steatosis is a major risk factor for metabolic and cardiovascular disease. Fat reduced hypocaloric diets are able to relieve the liver from ectopically stored lipids. We hypothesized that the widely used low carbohydrate hypocaloric diets are similarly effective in this regard. A total of 170 overweight and obese, otherwise healthy subjects were randomized to either reduced carbohydrate (n = 84) or reduced fat (n = 86), total energy restricted diet (-30% of energy intake before diet) for 6 months. Body composition was estimated by bioimpedance analyses and abdominal fat distribution by magnetic resonance tomography. Subjects were also submitted to fat spectroscopy of liver and oral glucose tolerance testing. In all, 102 subjects completed the diet intervention with measurements of intrahepatic lipid content. Both hypocaloric diets decreased body weight, total body fat, visceral fat, and intrahepatic lipid content. Subjects with high baseline intrahepatic lipids (>5.56%) lost ≈7-fold more intrahepatic lipids compared with those with low baseline values (<5.56%) irrespective of diet composition. In contrast, changes in visceral fat mass and insulin sensitivity were similar between subgroups, with low and high baseline intrahepatic lipids. CONCLUSION: A prolonged hypocaloric diet low in carbohydrates and high in fat has the same beneficial effects on intrahepatic lipid accumulation as the traditional low-fat hypocaloric diet. The decrease in intrahepatic lipids appears to be independent of visceral fat loss and is not tightly coupled with changes in whole body insulin sensitivity during 6 months of an energy restricted diet.