Does Physical Activity Regulate Appetite?

Do low activity levels lead to over eating?

Sixty years ago, researcher Jean Mayer worked on questions like this and published results from studies performed on mice, rats, and humans. (Science 1953; 117:504-5Am J Physiol 1954; 177:544-9Am J Clin Nutr 1956:169-75)

His work showed that inactive rodents and humans actually tend to eat more than their active counterparts. A reasonable hypothesis is that low levels of physical activity dysregulate appetite, or somehow trigger the desire to eat more.

If true, working hard isn’t the only way to work up an appetite. Unfortunately, not working works up an appetite, too.

Now, a study recently published in The Journal of Clinical Nutrition helps add to the present body of research. It’s descriptive title is Low levels of physical activity are associated with dysregulation of energy intake and fat mass gain over 1 year.

Data was tracked for a year, with participants divided into 5 groupings, based on how much moderate to vigorous physical activity they performed daily. Group 1 did the least amount of activity with 6 to 26 minutes per day. Group 5 did the most at 2 to 4 hours per day.

As it turned out body weight and BMI tracked inversely with these groupings. Group 1 (lowest activity) had the highest BMI, followed by Group 2, and so on, with Group 5 (highest activity) having the lowest BMI.

Chart: body weight to activity.

The chart for food consumption was not linear, though:

Chart: calorie intake

For groups 2, 3, 4, and 5, it could be said that as calorie consumption increased so did activity levels. Or, the other way around, as activity levels increased, so did calorie consumption. Harmony.

But, Group 1—with the highest BMI and lowest activity level—throws a wrench in the spokes. They were eating about as much as the more active Group 4 (1-2 hours per day of moderate to vigorous physical activity).

Just to be clear, in addition to being the most physically active, Group 5 was also eating the most and had the lowest bodyweight, BMI, and fat mass. They probably bought the most head- and wristbands, too, but the study didn’t track 80’s fitness gear.

headband and wristbands

The study’s results did line up nicely with Mayer’s work from back in the 1950s, though. The researchers noted:

…energy intake only increased proportionally with energy expenditure within a certain range of physical activity, which Mayer described as the “normal activity zone,” later described by Blunder et al as the “zone of regulation.” Below this level, the relation between intake and expenditure became uncoupled, resulting in energy imbalance.

An interesting finding of the new study was that the two groups with the lowest activity levels and highest BMIs (Groups 1 & 2) had the highest odds of gaining additional fat mass over 1 year. Surprisingly, the wristband crew didn’t win in this category…the groups with the highest activity levels (Groups 4 & 5) had higher odds of gaining fat mass compared to the group right in the middle (Group 3).

It would seem that Group 3 was in the sweet spot. If the zone of regulation truly exists, Group 3 was the most dialed in.

Ultimately, this study suggests that physical activity helps regulate bodyweight, not only by burning calories but also by helping to regulate appetite. The researchers commented:

This has important public health implications; in the present study, individuals in the middle quintile of activity performed 7,116 steps per day, a level of activity easily attainable by most adults.

They conclude that this level of activity prevents weight gain. Here a few of my  thoughts…

  • Those in Group 1 who were doing the least amount of activity, were tracked performing 6,062 steps per day ±1,778 steps. That works out to a  range of 4,284 – 7,840 steps—more than I would have expected. This means that on the higher end of the range, they were right there with Group 3’s average of 7,116 steps, and even beyond it. That seems contradictory to the conclusion of the researchers, but remember, Group 1 was only doing 6 to 26 minutes of moderate to vigorous physical activity per day; Group 3 did 40 to 90 minutes.
  • If you’d like to try regulating your appetite with physical activity, as this study suggests you can, try setting a daily goal of 7,000 steps using your smartphone or a pedometer—but remember to walk at a fast pace. This web page will help you determine the proper heart rate for moderate to vigorous physical activity, if you’d like to be sure.
  • The study also focused a bit on food cravings. They found that individuals in the lowest activity group had “significantly higher cravings for savory foods (French fries, burgers, pizza, etc.)” and that no other differences were observed for other items.

The study does a good job of discussing it’s own strengths and weaknesses. Like all studies, observational or otherwise, it’s far from perfect. Notably, the results are in line with the greater body of research, and hey, 7,000 steps really is achievable—and I’d say well worth trying for bodyweight maintenance. The only difficult step is that first one out the door.  After that, it’s as easy as…walking.

For weight loss, I suggest combining this strategy with a  way of eating to satiety that puts you in a calorie deficit. Eat, walk, and be merry!