Exercise increases the proportion of fat utilization during short-term consumption of a high-fat diet

Abstract

Amounts of exercise consistent with the Institute of Medicine's recommendations reduce the time required to match fat oxidation to a change in the percentage of fat in the diet. Because short-term consumption of high-fat diets is thought to contribute to excess fat accumulation, regular exercise should be protective and should help maintain a healthy body composition.

Influence of dietary fatty acid composition and exercise on changes in fat oxidation from a high-fat diet

“…Each study visit was separated by at least 2 wk. Before participation in the four study visits, subjects underwent a physical exam and screening, which has been described in detail previously (6). Briefly, resting metabolic rate (RMR; kcal/day) was measured for 30 min on the Deltatrac II Metabolic Monitor (VIASYS Healthcare, SensorMedics, Yorba Linda, CA) following an overnight fast.…”

“…The design of the metabolic chamber at the CTRC was similar in design to the chamber in the Department of Human Biology at Maastricht University in Maastricht, The Netherlands (25), and the specifications and diagnostics have been previously described (34). Additionally, information on chamber temperature, humidity, airflow, pressure, and data collection instrumentation has been described elsewhere (6). Briefly, the composition of air is measured with carbon dioxide (Hartman and Braun Uras-4) and oxygen (Magnos-6) gas analyzers (Applied Automation, Bartlesville, OK).…”

“…This is generally assumed to be caused by periods of positive energy balance resulting in the storage of fat but can also occur from short periods of positive fat balance even under eucaloric feeding conditions if, as hypothesized by Flatt, the weak human leptin system is overpowered by the stronger carbohydrate balance system leading to positive energy balance during the days following the period of positive fat balance (5). We and others have studied conditions that lead to a short-term positive fat balance and have shown that a shift to a high-fat (HF) diet from an average fat diet is not accompanied by an immediate increase in fat oxidation that would match the rate of fat intake even when the diets are eucaloric (6,27,28). The rate of fat oxidation increases only slowly with time, and thus it can be 5-7 days before fat balance is established on the HF diet.…”

“…The rate of fat oxidation increases only slowly with time, and thus it can be 5-7 days before fat balance is established on the HF diet. Investigators have previously studied the body's response to a HF diet [by assessing fat oxidation, nonprotein respiratory exchange ratio (NPRER), and 24-h energy expenditure (24hEE)] during exercise and sedentary conditions (6,14,26,29). Smith et al (29) reported that when six lean, healthy men switched from a standard American diet (37% energy as fat) to a HF diet (50% of energy as fat), NPRER was decreased while fat oxidation increased during a 5-day study.…”

“…Smith et al (29) reported that when six lean, healthy men switched from a standard American diet (37% energy as fat) to a HF diet (50% of energy as fat), NPRER was decreased while fat oxidation increased during a 5-day study. In a subsequent report, Hansen et al (6) examined the effects of a HF diet in female subjects during sedentary or exercise conditions. They found that exercise allowed the body to adjust more quickly to a HF diet by increasing 24-h fat oxidation more than during sedentary conditions.…”