Activity energy expenditure is a major determinant of dietary fat oxidation and trafficking, but the deleterious effect of detraining is more marked than the beneficial effect of training at current recommendations.

BACKGROUND: Previous studies suggested that physical activity energy expenditure (AEE) is a major determinant of dietary fat oxidation, which is a central component of fat metabolism and body weight regulation. OBJECTIVE: We tested this hypothesis by investigating the effect of contrasted physical activity levels on dietary saturated and monounsaturated fatty acid oxidation in relation to insulin sensitivity while controlling energy balance. DESIGN: Sedentary lean men (n = 10) trained for 2 mo according to the current guidelines on physical activity, and active lean men (n = 9) detrained for 1 mo by reducing structured and spontaneous activity. Dietary [d31]palmitate and [1-¹³C]oleate oxidation and incorporation into triglyceride-rich lipoproteins and nonesterified fatty acid, AEE, and muscle markers were studied before and after interventions. RESULTS: Training increased palmitate and oleate oxidation by 27% and 20%, respectively, whereas detraining reduced them by 31% and 13%, respectively (P < 0.05 for all). Changes in AEE were positively correlated with changes in oleate (R² = 0.62, P < 0.001) and palmitate (R² = 0.66, P < 0.0001) oxidation. The d31-palmitate appearance in nonesterified fatty acid and very-low-density lipoprotein pools was negatively associated with changes in fatty acid translocase CD36 (R² = 0.30), fatty acid transport protein 1 (R² = 0.24), and AcylCoA synthetase long chain family member 1 (ACSL1) (R² = 0.25) expressions and with changes in fatty acid binding protein expression (R² = 0.33). The d31-palmitate oxidation correlated with changes in ACSL1 (R² = 0.39) and carnitine palmitoyltransferase 1 (R² = 0.30) expressions (P < 0.05 for all). Similar relations were observed with oleate. Insulin response was associated with AEE (R² = 0.34, P = 0.02) and oleate (R² = 0.52, P < 0.01) and palmitate (R² = 0.62, P < 001) oxidation. CONCLUSION: Training and detraining modified the oxidation of the 2 most common dietary fats, likely through a better trafficking and uptake by the muscle, which was negatively associated with whole-body insulin sensitivity.

Diet and physical activity profiles in French preadolescents.

Dietary patterns have been identified in adults, but less is known about children and adolescents. For the first time, we have investigated lifestyle patterns combining diet and physical activity in 12-year-old French preadolescents and examined their association with sociodemographic factors. Physical activity, sedentary activities and dietary habits were assessed by questionnaires given to 2724 students in 2001. Family income tax and parents' educational level, as indicators of socio-economic status, and the size of the residence commune were obtained from parents. After adjusting for socio-economic status, physical activity was positively associated with a consumption of fruit/vegetables/fruit juice on more than four occasions in the previous 24 h (P<0.001). Sedentary activities were positively associated with the consumption of French fries or potato chips (P<0.001), with sweetened drink as the most usual drink (P<0.001) and with nibbling while watching television (P<0.001), and inversely associated with a high consumption of fruit/vegetables/fruit juice (P=0.04). Multiple correspondence analysis identified two independent axes and specific combinations of behaviour: one axis characterised by sedentary activity, sweetened drink as the most usual drink, the consumption of French fries or potato chips and nibbling while watching television; a second one associating physical activity and the consumption of fruit/vegetables/fruit juice. Both socio-economic proxies were associated with the former axis (P<0.001). The size of the residence commune was associated with the latter (P<0.1). Combinations of diet and physical activity habits were identified in adolescents, indicating that prevention programmes targeting both behaviours may have an enhanced outcome.