Effect of Calorie Restriction With or Without Exercise on Insulin Sensitivity, Β-Cell Function, Fat Cell Size, and Ectopic Lipid in Overweight Subjects

• Published in: Diabetes care Vol. 29; no. 6; pp. 1337 - 1344
• Main Authors: Larson-Meyer, D. Enette, Heilbronn, Leonie K, Redman, Leanne M, Newcomer, Bradley R, Frisard, Madlyn I, Anton, Steve, Smith, Steven R, Alfonso, Anthony, Ravussin, Eric
• Format: Journal Article
• Language: English
• Published: Alexandria, VA American Diabetes Association 01.06.2006
• Subjects: adipocytes; adipose tissue; Adipose Tissue - pathology; Basal Metabolism; Biological and medical sciences; body fat; Body Mass Index; Body Weight; Cell Size; Diabetes; Diabetes. Impaired glucose tolerance; Diet, Reducing; Endocrine pancreas. Apud cells (diseases); Endocrinopathies; energy expenditure; Energy Metabolism; energy requirements; Exercise; Health aspects; Humans; Insulin; Insulin - physiology; insulin resistance; Islets of Langerhans - physiopathology; Lipids - blood; liver; low calorie diet; Medical sciences; Metabolic diseases; Obesity; Overweight; Risk factors; Viscera; volunteers; weight control; weight loss; Physical exercise; Human; Adipocyte; Pancreatic hormone; Adipose tissue; Liver; Langerhans islet; Lipids; Insulin; Overweight; Sensitivity; Muscle; β Cell; Endocrine pancreas; Low calorie diet
• ISSN: 0149-5992; 1935-5548
• DOI: 10.2337/dc05-2565

OBJECTIVE:--The purpose of this article was to determine the relationships among total body fat, visceral adipose tissue (VAT), fat cell size (FCS), ectopic fat deposition in liver (intrahepatic lipid [IHL]) and muscle (intramyocellular lipid [IMCL]), and insulin sensitivity index (Si) in healthy overweight, glucose-tolerant subjects and the effects of calorie restriction by diet alone or in conjunction with exercise on these variables. RESEARCH DESIGN AND METHODS--Forty-eight overweight volunteers were randomly assigned to four groups: control (100% of energy requirements), 25% calorie restriction (CR), 12.5% calorie restriction +12.5% energy expenditure through structured exercise (CREX), or 15% weight loss by a low-calorie diet followed by weight maintenance for 6 months (LCD). Weight, percent body fat, VAT, IMCL, IHL, FCS, and Si were assessed at baseline and month 6. RESULTS:--At baseline, FCS was related to VAT and IHL (P < 0.05) but not to IMCL. FCS was also the strongest determinant of Si (P < 0.01). Weight loss at month 6 was 1 ± 1% (control, mean ± SE), 10 ± 1% (CR), 10 ± 1% (CREX), and 14 ± 1% (LCD). VAT, FCS, percent body fat, and IHL were reduced in the three intervention groups (P < 0.01), but IMCL was unchanged. Si was increased at month 6 (P = 0.05) in the CREX (37 ± 18%) and LCD (70 ± 34%) groups (P < 0.05) and tended to increase in the CR group (40 ± 20%, P = 0.08). Together the improvements in Si were related to loss in weight, fat mass, and VAT, but not IHL, IMCL, or FCS. CONCLUSIONS:--Large adipocytes lead to lipid deposition in visceral and hepatic tissues, promoting insulin resistance. Calorie restriction by diet alone or with exercise reverses this trend.