Immunological effects of low-fat diets with and without weight loss.
OBJECTIVE
The immunologic effects of isocaloric reduced- and low-fat diets and a voluntary calorie-restricted low-fat diet resulting in weight loss were compared to the immunologic effects of an average American diet in hyperlipidemic individuals.


METHODS
Ten hyperlipidemic subjects were studied during three six-week weight maintenance phases: baseline (BL) [35% fat [14% saturated fat (SFA), 13% monounsaturated fat (MUFA), 8% polyunsaturated fat (PUFA)] and 147 mg cholesterol (C)/1000 kcal], reduced-fat (RF) [26% fat (4% SFA, 11% MUFA, 11% PUFA) and 45 mg C/1000 kcal], and low-fat (LF) [15% fat (5% SFA, 5% MUFA, 3% PUFA) and 35 mg C/1000 kcal] diets followed by 12-week, low-fat calorie reduced phase (LFCR).


RESULTS
During the last phase, the subjects' weight significantly decreased (p = 0.005). Cholesterol levels were significantly reduced during all phases, compared to BL diet (p < 0.05). Delayed-type hypersensitivity (DTH) was assessed using Multi-test CMI. Maximum induration diameters were 22.7, 25.4, 30.5, 34.5 mm for BL, RF, LF and LFCR diets, respectively. Subjects on the LFCR diets had significantly higher DTH compared to the BL diet (p = 0.005). No significant effect of diet was observed on lymphocyte proliferation or interleukin (IL)-1, IL-2 and prostaglandin (PG) E(2) production.


CONCLUSIONS
These data suggest that low-fat diets (15% energy), under conditions which result in weight loss, do not compromise and may enhance the immune response of middle-aged and elderly hyperlipidemic subjects. The results of this study provide support for the hypothesis that moderate caloric restriction in humans may have a beneficial effect on cell-mediated immunity such as those reported in calorie-restricted rodents.
Santos
Michelle S
MS
Nutritional Immunology Laboratory, Jean Mayer USDA Human Nutrition Research Center on Aging, Tufts University, 711 Washington Street, Boston, MA 02111, USA.
Lichtenstein
Alice H
AH
Leka
Lynette S
LS
Goldin
Barry
B
Schaefer
Ernst J
EJ
Meydani
Simin Nikbin
SN
D000368:Aged; D002784:Cholesterol / Q000097:blood*; D018592:Cross-Over Studies; D018752:Diet, Fat-Restricted; D004038:Diet, Reducing; D004041:Dietary Fats / Q000008:administration & dosage*; D005260:Female; D006801:Humans; D006949:Hyperlipidemias / Q000178:diet therapy* / Q000276:immunology; D006968:Hypersensitivity, Delayed; D007111:Immunity, Cellular / Q000187:drug effects; D008297:Male; D008875:Middle Aged; D015431:Weight Loss / Q000276:immunology*
D004041:Dietary Fats; D002784:Cholesterol