Effects of isoenergetic, low-fat diets on energy metabolism in lean and obese women.

Whether changing from a high-fat diet to an isoenergetic, low-fat, high-complex-carbohydrate diet results in thermogenic benefits is controversial. Brief dietary interventions and failure to account for the potential influence of body-fat distribution on energy metabolism could have confounded the interpretation of previous studies. To address these issues, eight upper-body obese, seven lower-body obese, and eight non-obese premenopausal women underwent measurements of body composition, resting energy expenditure, overnight energy expenditure, and meal fat oxidation at the end of a weight-stabilizing, high-fat (42%) diet, and after 4 wk of an isoenergetic, low-fat (27%) diet. No change in body composition, resting energy expenditure, overnight energy expenditure, or meal fat oxidation occurred. We conclude that isoenergetic shifts from dietary fat to dietary carbohydrate within the generally recommended range have little or no effect on energy metabolism, and that body-fat distribution does not predict differences in energy expenditure.

Nutritional support for liver transplantation: identifying caloric and protein requirements.

OBJECTIVE: To characterize the caloric and protein requirements of patients with end-stage liver disease before and for 28 days after liver transplantation. DESIGN: We prospectively assessed 16 adult patients who were scheduled to undergo liver transplantation between December 1989 and September 1990. MATERIAL AND METHODS: Nitrogen balance, 24-hour urinary creatinine, 3-methylhistidine, and resting energy expenditure were determined before transplantation and on days 1, 3, 5, 14, and 28 after transplantation. The investigators were unaware of the results of these measurements, and patients were fed in accordance with a previously established clinical protocol. RESULTS: Resting energy expenditure did not increase from preoperative values; however, urinary nitrogen and 3-methylhistidine increased significantly after liver transplantation, an indication of protein catabolism from a myofibrillar source. A negative nitrogen balance persisted for 28 days post-operatively. CONCLUSION: We recommend that caloric intake be determined by using the formulation provided by the Harris-Benedict equation at ideal body weight plus 20%. We also recommend that intake of protein be adjusted on the basis of preoperative nutritional assessment, perioperative hepatic and renal function, and results of tests used to measure the adequacy of administered protein. Parenterally or enterally administered protein of more than 1.2 g/kg daily should be well tolerated in most patients who have undergone liver transplantation.