Intramyocellular lipid variations in active older men: relationship with aerobic fitness.

AIMS: Intramyocellular lipid (IMCL) variations in older men are poorly explored. In young adults, IMCL can be influenced by both diet and exercise interventions; this flexibility is related to aerobic fitness. We evaluated in active older adults the influence of maximal aerobic capacity on short-term diet and exercise-induced variations in IMCL stores. METHODS: Intramyocellular lipids were measured by (1) H magnetic resonance spectroscopy ((1) H-MRS) after a 3-day fat depletion-replenishment diet (IMCL(FDR) ) and immediately after a 2-h exercise at 50% VO(2) max (IMCL(FDR) (_) (EX) ). To further explore diet influence, the protocol was repeated after a high-fat diet (HF), with both pre- and post-exercise measurements (IMCL(HF) and IMCL(HF) (_) (EX) ). RESULTS: In active older men (69.8 ± 5.2 years), IMCL(FDR) was lowered by exercise (IMCL(FDR) = 3.45 ± 1.52 vs. IMCL(FDR) (_) (EX) = 2.74 ± 1.15 mmol kg(-1) wet weight, P < 0.05), and exercise-induced variations were correlated to the initial store (P < 0.05, r = -0.72). IMCL(FDR) was linked with aerobic fitness (P < 0.05, r = 0.76), when adjusted by fat mass. IMCL(HF) was lower than IMCL(FDR) (P < 0.05), decreased after exercise (P < 0.05) and varied also as a function of initial store (P < 0.05, r = -0.89), but without link with aerobic fitness. Finally, diet-induced IMCL store variations were positively linked to aerobic fitness (P < 0.05, r = 0.89). CONCLUSION: Variations of the IMCL stores in physically active older adults appear related to aerobic fitness, with similarly fast adaptation to short-term interventions combining diet and exercise as young active adults.

Subcutaneous adipose tissue remodeling during the initial phase of weight gain induced by overfeeding in humans.

CONTEXT: Deciphering the early processes occurring in adipose tissue during weight gain is a major issue for understanding the development of fat mass and obesity. Experimental overfeeding in humans is a unique situation to tackle these events. OBJECTIVE: Our aim was to identify the pathways involved in sc adipose tissue remodeling during the initial phase of weight gain. RESEARCH DESIGN AND METHODS: Forty-four healthy men were involved in an overfeeding protocol with a lipid-enriched diet (+760 kcal/d) for 2 months. Subcutaneous abdominal adipose tissue biopsies were taken for histology, transcriptomics, and Western blotting in the basal state, after 14 d, and at the end of the protocol. RESULTS: Overfeeding significantly increased body weight (+2.5 kg) and fat mass. Reorganization of gene expression patterns occurred in adipose tissue with an up-regulation of numerous genes involved in lipid metabolism and storage, followed by clusters of genes related to angiogenesis and extracellular matrix remodeling. Histological examination showed increased microvascular density and connective tissue deposition after 56 d of overfeeding, with no changes in the number of macrophages or inflammatory cells. Inhibition of the canonical Wnt/ß-catenin signaling pathway and induction of the renin-angiotensin system might be implicated in the remodeling of sc adipose tissue. CONCLUSIONS: We characterize the coordinated and time-dependent processes that occur in human adipose tissue during the early phase of weight gain in healthy subjects and identify pathways representing potential targets in pathologies of adipose development, including obesity.

Is advice for breakfast consumption justified? Results from a short-term dietary and metabolic experiment in young healthy men.

Short-term (2 weeks) effects of the consumption of a high-energy (2920 kJ (700 kcal)) or low-energy (418 kJ (100 kcal)) breakfast on dietary patterns, blood variables and energy expenditure (indirect calorimetry) were compared in ten free-living healthy young men in a crossover study. During the high-energy breakfast, total energy intake was increased, the intake of protein and lipids was unchanged but the intake of carbohydrates was increased. Thus, 48 (sd 4)% of energy came from carbohydrates in the high-energy breakfast compared with 42 (sd 5)% in the low-energy breakfast. Excluding breakfast, the macronutrient composition of the diet remained identical in the two situations. After the high-energy breakfast, fasting serum triacylglycerol concentration was higher and HDL-cholesterol concentration was lower than after the low-energy breakfast. A high glycaemic response was observed in the morning after the high-energy breakfast period, while there was a peak of free fatty acids after the low-energy breakfast. The high-energy breakfast induced a strong inhibition of fat oxidation throughout the day. Although long-term adaptation to a high-energy breakfast cannot be excluded, the high-energy breakfast in this study did not appear to be favourable to health. Our results do not support the current advice to consume more energy at breakfast.