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

Abstract

THE PENNINGTON CALERIE TEAMOBJECTIVE -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 (S i ) 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 ϩ12.5% 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 S i were assessed at baseline and month 6. RESULTS -At baseline, FCS was related to VAT and IHL (P Ͻ 0.05) but not to IMCL. FCS was also the strongest determinant of S i (P Ͻ 0.01). Weight loss at month 6 was 1 Ϯ 1% (control, mean Ϯ SE), 10 Ϯ 1% (CR), 10 Ϯ 1% (CREX), and 14 Ϯ 1% (LCD). VAT, FCS, percent body fat, and IHL were reduced in the three intervention groups (P Ͻ 0.01), but IMCL was unchanged. S i was increased at month 6 (P ϭ 0.05) in the CREX (37 Ϯ 18%) and LCD (70 Ϯ 34%) groups (P Ͻ 0.05) and tended to increase in the CR group (40 Ϯ 20%, P ϭ 0.08). Together the improvements in S i 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.

Allometric relationship between changes of visceral fat and total fat mass

“…The number of men and women was not reported for 3% of the subjects. These studies investigated a wide range of weight-loss interventions including caloric restriction, 9,11,13,14,16,17,19,[20][21][22][23] 10,18,24 One study reported data from women with type 2 diabetes 17 and another study investigated HIV-positive women. 15 We plotted the loss of visceral fat mass relative to the total loss of fat mass (DVAT/DFM) against the initial visceral fat mass divided by the total fat mass (VAT/FM).…”

The diagnosis and management of non-alcoholic fatty liver disease: Practice Guideline by the American Association for the Study of Liver Diseases, American College of Gastroenterology, and the American Gastroenterological Association

“…The results from these studies using a variety of interventions, either by diet alone 81,83,84,89,92,93 or in combination with different exercise prescriptions, 82,[85][86][87][88]92,94 have consistently reported a significant reduction in liver fat by an average of $40% (ranging from 20% to 81%). The degree of hepatic fat reduction was proportional to the intensity of the lifestyle intervention and generally required a body weight loss between $5 to 10%.…”

Dietary restriction and the pursuit of effective mimetics

“…However, what is unequivocal is that DR induces significant health benefits in many animals, and arguably what is really important is a greater period of total life free from age-related disease rather than an extension of lifespan per se. In human subjects, it is evident that even shortterm and relatively moderate DR in overweight and obese individuals, and in non-obese individuals, can confer a multitude of health benefits (75)(76)(77)(78) . For example, DR appears to protect against a range of age-related diseases in human subjects, including obesity, CVD, arteriosclerosis and hypertension (75)(76)(77)(78)(79)(80)(81) .…”

“…In human subjects, it is evident that even shortterm and relatively moderate DR in overweight and obese individuals, and in non-obese individuals, can confer a multitude of health benefits (75)(76)(77)(78) . For example, DR appears to protect against a range of age-related diseases in human subjects, including obesity, CVD, arteriosclerosis and hypertension (75)(76)(77)(78)(79)(80)(81) . DR also slows age-related declines in left ventricular diastolic function, increases insulin sensitivity and reduces the levels of several inflammatory cytokines (75) .…”