The effects of marked caloric restriction on lipoprotein lipase-activators in obese subjects

Changes in plasma lipoproteins during low-fat, high-carbohydrate diets: effects of energy intake

BACKGROUND

Low-fat diets can increase plasma triacylglycerol and reduce HDL cholesterol. Changes in energy intake and body weight can influence the lipoprotein response.

OBJECTIVE

We sought to prospectively examine the effects of euenergetic and ad libitum dietary fat restriction on plasma lipoproteins in healthy postmenopausal women.

DESIGN

Participants first received a controlled euenergetic diet in which dietary fat was reduced stepwise from 35% to 25% to 15% over 4 mo. Thereafter, participants followed an ad libitum 15%-fat diet for 8 mo; 54 women completed the intervention.

RESULTS

During the controlled euenergetic diet, plasma triacylglycerol increased from 1.70 +/- 0.10 to 2.30 +/- 0.16 mmol/L, total cholesterol decreased from 5.87 +/- 0.13 to 5.53 +/- 0. 13 mmol/L, LDL cholesterol decreased from 3.41 +/- 0.10 to 2.87 +/- 0.10 mmol/L, HDL cholesterol decreased from 1.76 +/- 0.08 to 1.50 +/- 0.08 mmol/L, and apolipoprotein (apo) A-I decreased from 5.11 +/- 0.14 to 4.78 +/- 0.14 mmol/L (P < 0.0001 for all changes). Hormone replacement therapy did not affect the relative change in HDL cholesterol. Plasma glucose, insulin, hemoglobin A(1C,) free fatty acid, and apo B concentrations did not change significantly. During the ad libitum 15%-fat diet, participants lost 4.6 +/- 0.4 kg. Plasma triacylglycerol and LDL cholesterol returned to baseline values (1.77 +/- 0.12 and 3.31 +/- 0.08 mmol/L, respectively), whereas HDL cholesterol and apo A-I remained low (1.40 +/- 0.08 and 4.82 +/- 0.18 mmol/L, respectively). HDL cholesterol and apo A-I concentrations stabilized in subjects who were not receiving hormone replacement therapy but continued to decline in women who were receiving hormone therapy.

CONCLUSIONS

The ad libitum 15%-fat diet resulted in significant weight loss. The euenergetic but not the ad libitum diet caused hypertriacylglycerolemia. HDL cholesterol decreased during both low-fat diets.

Hypertension, hormones, and aging

The most rapidly growing segment of the United States population is the geriatric group, especially those above 75 years of age. Hypertension, diabetes mellitus, and dyslipidemia increase with advancing years in Westernized, industrialized societies such as the United States. These disorders contribute significantly to strokes and myocardial infarctions and associated morbidity and mortality in our elderly population. The increase in these chronic disease processes with aging is related, in part, to increasing obesity, reductions in physical activity, and medications that predispose to these conditions (ie, nonsteroidal inflammatory agents and hypertension). Hypertension in the elderly is characterized by high peripheral vascular resistance/reduced cardiac output, impaired baroflex sensitivity, relatively greater systolic pressures, increased blood pressure variability, and a propensity to salt sensitivity. Type 2 diabetes in the elderly is related to alterations in body composition (ie, increased central adiposity and decreased lean body mass) and to reduced physical activity. There is an increasing body of evidence that aggressive treatment of hypertension and dyslipidemia in the elderly results in comparable, if not greater, reductions in cardiovascular morbidity and mortality in the elderly as in younger counterparts.