For over 30 years, I’ve been going to Oakland A’s baseball games with one of my best friends. We live in different cities and have busy lives, so we don’t get to see games together as frequently as we used to.

After several years, we finally met up again last weekend to see a game. Although we’ve both changed a lot over the years, some things never change. Now in his 40s, my friend continues to stay remarkably lean despite trading competitive swimming for marriage, parenthood, and a busy career well over a decade ago. His only exercise is yoga, a few times a week.

And just like when we were in high school, he amazed me by opening his backpack and pulling out a giant bag of pistachios, fruit, PB&J sandwiches, and a box of graham crackers to eat before running to the concessions stand to buy ice cream and other snacks.

How does a guy who eats so much stay so lean, we wondered. After a little while, the answer became clear. I watched as he stood up and cheered then sat back down. He turned his head to watch the scoreboard and video screen, nudged me to look at what he saw, and pointed to direct me. He leaned forward, opened his bag of food, leaned back, picked up his phone, put it down again, opened a box of food, stood up to brush off his jeans, and sat back down again. During all of this, I sat without moving.

It all made sense. I turned to him and said, “You stay lean because you’re a mover.”

NEAT Research

Mayo Clinic endocrinologist and obesity expert, Dr. James Levine, has examined what I call movers for over a decade. He believes that engaging in more frequent exercise is not the answer to the problem of excess body fat. Instead, nonexercise activity is the key variable.

Levine coined the term, NEAT (nonexercise activity thermogenesis) to refer to energy used during activities that wouldn’t normally be considered exercise. Examples include gardening, shopping, walking around the house, or even fidgeting.

Here’s why NEAT is so important: The energy from food we eat is used 1) to maintain essential functions of the body, 2) for digestion, and 3) to support activity. Activity is the domain in which we see the greatest individual differences. Some people are highly active; others not so much. Exercising more is one way to deal with excess stored energy (body fat), but this is not practical or desirable for most people. Increasing nonexercise activity is much more realistic.

Levine estimates that NEAT can account for anywhere from 15% to 50% of energy expenditure, which is fascinating when you consider the potential for fat loss or weight management associated with merely increasing low-intensity activities each day.

Levine and his colleagues conducted three studies on NEAT that I find particularly interesting. Collectively, these studies reveal

• the most important reason not everyone gets fat from overeating
• the behavioral differences between lean and obese nonexercisers
• how increasing NEAT can treat obesity

Here are summaries of the three studies.

Responses to Overfeeding

There is evidence to suggest that NEAT contributes more to fat loss than we might expect. In a classic study, Levine et al. (1999) selected 16 nonobese adults who were “overfed” by systematically increasing their dietary intake by exactly 1000 kcal/day. The researchers were able to account for the fate of 97% of the excess, which went either to storage (e.g., body fat) or dissipation (e.g., burned through activity).

Participants were instructed not to engage in exercise and compliance was assessed through journaling. The data indicated that fat gain was inversely related to NEAT. In other words, participants who increased their low-intensity activity gained little to no body fat even when overfed. In the scatterplot below, you can see how, among these overfed participants, the ones who spontaneously increased their nonexercise activity level gained almost no body fat.

The Problem of Sitting

To determine the extent to which NEAT contributes to differences in body fatness, Levine et al. (2005), selected 10 lean and 10 mildly obese individuals who identified as “couch potatoes,” due to their lack of involvement in exercise. Participants wore underwear with sensors to record their movements over a 10-day period. These highly sensitive activity monitors were able to detect changes in position and movement 120 times per minute. As indicated in the graph below, obese participants spent more time sitting each day and lean participants spent more time standing or moving. The mean differences between the groups in standing/moving and sitting were more than 2 ½ hours. The authors estimated the caloric cost of this difference to be about 350 kcals.

A NEAT Intervention

One way to increase NEAT is by walking. Most of us could benefit from walking more each day. In a clever intervention study targeting obesity, participants were given treadmill desks so they could stand and walk slowly instead of sitting while working (Levine & Miller, 2007). The mean energy expenditure while seated was 72 kcal/hour; the mean energy expenditure while walking 1 mph (a very slow pace to accommodate typing) was 191 kcal/hour. The authors concluded that “if obese individuals were to replace time spent sitting at the computer with walking computer time by 2-3 h/day, and if other components of energy balance were constant, a weight loss of 20-30 kg/year could occur.”

Read more about Dr. James Levine’s research in his book, Move a Little, Lose a Lot.

Summary

• Minimal involvement in low-intensity, nonexercise activity may the most important contributor to obesity.
• Time spent sitting distinguishes lean and obese groups. The difference is 2 to 3 hours.
• Obesity could theoretically be eliminated merely by increasing daily nonexercise activity.

Sources:

Levine, J. A., Eberhardt, N. L., & Jensen, M. D. (1999). Role of nonexercise activity thermogenesis in resistance to fat gain in humans. Science, 283, 212-214.

Levine, J. A., & Miller, J. M. (2007). The energy expenditure of using a “walk-and-work” desk for office workers with obesity. British Journal of Sports Medicine, 41, 558-561.

Levine, J. A., Lanningham-Foster, L. M., McCrady, S. K., Krizan, A. C., Olson, L. R., Kane, P. H., Jensen, M. D., & Clark, M. M. (2005). Interindividual variation in posture allocation: Possible role in human obesity. Science, 307, 584-586.