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Insufficient activity blunts our metabolic response to exercise

Background

Exercise can improve glucose and triglyceride levels following a meal, but there’s evidence that sedentary behavior may blunt, or entirely negate, these metabolic benefits. Some studies have shown that the number of steps taken per day can predict this “exercise resistance”; how much do we need to move to get the metabolic perks of exercise?

The study

In this randomized crossover study, 10 participants completed three five-day interventions composed of two days of controlled activity, two days of step reduction, and one day without exercise but with a high-fat shake in the morning. The interventions were separated by a one-week washout period.

During the two days of controlled activity, the participants walked close to the imposed limit of 10,000 steps/day. They were then assigned to one of three step-count groups: 2 days of “low” (2,675 ± 314), “limited” (4,759 ± 276), or “normal” (8,481 ± 581) steps/day. When not walking, the participants were asked to stay seated or lying down. All the participants underwent all three interventions in random order.

On the evening of the second day, the participants jogged for one hour (their running steps were not counted in their total steps of the day). The next morning they consumed a high-fat shake, and their postprandial responses were compared at 2, 3, 4 and 6 hours.

The results

Compared to the “normal” group, the “low” and “limited” groups saw similar increases in postprandial triglycerides (+23%) at 2, 3, and 4 hours. Total body fat oxidation was significantly lower in the “low” (−19%) and “limited” (−14%) groups than in the “normal” group. Plasma glucose showed no difference between groups.

Overall, this study suggests that you need to walk more than a certain number of daily steps to overcome “exercise resistance” (a blunting of the metabolic benefits of daily exercise). How many steps are needed isn’t clear, but according to this study, about 8,000 is enough while 5,000 isn’t.

Note

This study highlights the importance of nonexercise physical activity throughout the day. If all the walking you ever do is from your doorstep to your car, those steps aren’t likely to benefit your health; but by walking instead of driving, or by spending a little more time walking your dog, you may accumulate enough steps to overcome “exercise resistance” and thereby make a real difference in your health. And if you do walk as a form of exercise too, your “exercise steps” and “nonexercise steps” will add up.

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