Effect of calorie restriction with or without exercise on insulin sensitivity, beta-cell function, fat cell size, and ectopic lipid in overweight subjects.
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 (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.


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 S(i) 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 S(i) (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. S(i) 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 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.
Larson-Meyer
D Enette
DE
Pennington Biomedical Research Center, 6400 Perkins Road, Baton Rouge, LA 70808, USA.
Heilbronn
Leonie K
LK
Redman
Leanne M
LM
Newcomer
Bradley R
BR
Frisard
Madlyn I
MI
Anton
Steve
S
Smith
Steven R
SR
Alfonso
Anthony
A
Ravussin
Eric
E
D000273:Adipose Tissue / Q000473:pathology*; D001481:Basal Metabolism; D015992:Body Mass Index; D001835:Body Weight; D048429:Cell Size; D004038:Diet, Reducing; D004734:Energy Metabolism; D015444:Exercise; D006801:Humans; D007328:Insulin / Q000502:physiology*; D007515:Islets of Langerhans / Q000503:physiopathology*; D008055:Lipids / Q000097:blood*; D050177:Overweight; D014781:Viscera
D007328:Insulin; D008055:Lipids