Brisk walking offsets the increase in postprandial TAG concentrations found when changing to a diet with increased carbohydrate

We tested the hypothesis that 30min of brisk walking daily would offset the increase in plasma TAG concentrations associated with substituting dietary fat for carbohydrate. Fourteen subjects (six males) aged 57 (sd 5) years underwent three 4d trials in a counterbalanced order: (i) 4d on a typical UK diet (40% energy from fat, 45% carbohydrate and 15% protein); (ii) 4d on an isoenergetic diet but substituting fat for carbohydrate in line with the present recommendations (30% fat, 55% carbohydrate and 15% protein); (iii) 4d on the same recommended diet with 30min of brisk walking each day. The food provided for the first 3d of each trial was isoenergetic with each volunteer's previously determined daily energy intake. On day 4, the subjects consumed breakfast, lunch and an early evening meal, equivalent in total to 90% of their daily energy intake. Blood samples were collected and substrate utilisation and energy expenditure were determined in the fasted state and for 9h postprandially. Substrate utilisation differed significantly among trials (P=0.003); RER was higher on the recommended diet trial than during either of the other two trials (P=0.012 and 0.021 for the UK diet and recommended diet with walking, respectively). The rise in plasma TAG concentrations over the day was steeper on the recommended diet trial than on the other two trials (trialtime interaction, P=0.040). The increase in postprandial TAG concentrations associated with substituting dietary fat for carbohydrate was offset by 30min of brisk walking daily.