Heli J. Roy | 10/29/2005 1:31:32 AM
Under healthy conditions, skeletal muscles oxidize fat. In type 2 diabetes and obesity, as well as after significant weight loss, however, that ability drops. A high-fat diet exacerbates the condition and results in a positive fat balance.
This reduced capacity to oxidative fat may be a predictor of weight gain, according to LSU AgCenter nutritionist Dr. Heli Roy.
Decreased adaptation to a high-fat diet has been found in obese individuals, those who have a family history of obesity and those who were previously obese, but lost weight. This may point to a genetic tendency as a reason that some individuals are inefficient fat oxidizers.
Roy explains that healthy, lean individuals use fat mainly as fuel at rest and switch to carbohydrates when insulin is released. Those who are insulin resistant, however, oxidize less fat at rest and do not respond to insulin as readily.
Muscle cell metabolism may be an intrinsic capacity that remains even if cells are removed from their original context. Doctors Barbara Ukrapova, Michele McNeil, Olga Sereda, Lilian de Jonge, Hui Xie, George Bray and Steven Smith from the Pennington Biomedical Research Center studied muscle cells from 16 healthy young men to find out if muscle cells maintained their identity when cultured in the lab.
Sixteen healthy young men, ages 18 to 29, with a range of body mass indexes (BMI = kg/m2) ranging from 20 to 35 and fat mass varying from 7.27 to 26.89 kg, were studied. The men followed a high-fat diet for three days. Insulin sensitivity was assessed before the men went on a high-fat diet. Cell cultures were collected before and during the high-fat diet.
Insulin sensitivity was related to body fat content. Those who had lower body fat had higher insulin sensitivity.
The ability to oxidize fat was higher in those who had lower body fat content and in those who did aerobic activity.
Those who had a high level of circulating fatty acids (indicating higher fat mass) were not as able to oxidize fatty acids as readily. They also were not as adaptable to switching to a high-fat diet but were more likely to be in a positive fat balance.
Roy says those who are poor fat oxidizers should follow a diet based on the USDA Dietary Guidelines and MyPyramid that have the following key recommendations:
• Consume less than 10 percent of calories from saturated fatty acids and less than 300 mg/day of cholesterol, and keep trans-fatty acid consumption as low as possible.
• Keep total fat intake between 20 percent to 35 percent of calories, with most fats coming from sources of polyunsaturated and monounsaturated fatty acids, such as fish, nuts and vegetable oils.
• When selecting and preparing meat, poultry, dry beans and milk or milk products, make choices that are lean, lowfat or fat free.
• Limit intake of fats and oils high in saturated and/or trans-fatty acids, and choose products low in such fats and oils.
For information on related nutrition, family and consumer topics, click on the Family and Home link at the LSU AgCenter Web site at www.lsuagcenter.com. For local information and educational programs, contact an extension agent in your parish LSU AgCenter office.
On the Internet: LSU AgCenter: http://www.lsuagcenter.com/
Source: Heli Roy (225) 578-3329, or HRoy@agcenter.lsu.edu