Why Diet and Exercise Work for Some but Not for Others
This is a response to Fat Obstetrics at Navelgazing Midwife, which was a response to a post about separate maternity facilities for obese pregnant women at The Unnecesarean and Exaggerating the Risks Again at The Well-Rounded Mama, which discussed an article in The New York Times arguing that Growing Obesity Increases Perils of Childbearing.
Diet & Exercise--the most common phrase whenever the topics of obesity and weight loss arise. At the end of the day, achieving or maintaining a healthy weight is simple: eat healthier and exercise more.
Or is it that simple?
The millions of people who have tried this approach, and failed, can testify that there's something going on besides calories in through food and calories expended through exercise.
Mayo Clinic endocrinologist James A. Levine has discovered a third major player--more important, even, than diet and exercise combined--in regulating weight levels. It's called NEAT, short for non-exercise activity thermogenesis. NEAT is the energy we expend in everyday activities such as fidgeting, cleaning, gardening, or cooking. When you're not sleeping or sitting, and when you're not actively exercising, you're producing NEAT. This short interview with All Things Considered explains the basics of NEAT:
Through a rigorous research study involving precisely calibrated meals, high-tech underwear, and $1,000 drinks to ensure study participants weren't "cheating" with outside foods, James Levine discovered that NEAT explains why some people weigh more and others less, despite similar levels of food intake and exercise. From his primer on NEAT:
For the vast majority of dwellers in the U.S., exercise activity thermogenesis is negligible. NEAT, even in avid exercisers, is the predominant constituent of activity thermogenesis and is the EE [energy expenditure] associated with all the activities we undertake as vibrant, independent beings....
NEAT is likely to contribute substantially to the inter- and intra-personal variability in EE. Argue thus; if three-quarters of the variance of BMR [basal metabolic rate] is accounted for by variance in lean body mass and, TEF [thermic effect of food ] represents 10-15 percent of total EE, then the majority of the variance in total EE that occurs independent of body weight must be accounted for by NEAT. Evidence supports this. NEAT is highly variable and ranges from ~ 15 percent of total daily EE in very sedentary individuals to >50 percent in highly active persons. Even minor changes in physical activity throughout the day can increase daily EE by 20 percent. NEAT is impacted by environment, but is also under biological control.
In other words, a person's level of exercise (running, swimming, biking, etc.) has only a small effect on her total energy expenditure and thus her body weight. Levine's research study found that overweight people expend far less NEAT than people at a normal body weight--even after they have lost weight. The reverse is true for lean people who gain weight artificially (i.e., on purpose for a research study such as Levine's). From a Mayo Clinic report of Levine's research:
NEAT — more powerful than formal exercise — determines who is lean, and who is obese. Obese persons sit, on average, 150 minutes more each day than their naturally lean counterparts. This means obese people burn 350 fewer calories a day than do lean people....
[Levine] adds that the NEAT defect in obese patients doesn't reflect a lack of motivation. "It most likely reflects a brain chemical difference because our study shows that even when obese people lose weight they remain seated the same number of minutes per day," says Dr. Levine. "They don't stand or walk more. And conversely, when lean people artificially gain weight, they don't sit more. So the NEAT appears to be fixed. But as physicians, we can use this data to help our obese patients overcome low NEAT by guiding the treatment of obesity toward a focus on energy as well as food. We can encourage NEAT-seeking behaviors."
Levine is actively involved in developing real-life, affordable solutions for increasing people's NEAT. Levine has built a working "treadmill office," complete with a 2-lane walking track that serves as the meeting room and desks equipped with treadmills rather than chairs. By walking at 0.7 mph instead of sitting at a desk, a person expends 800 additional calories per day just by going to work.
If you want to learn more about NEAT and how to incorporate it into your everyday routines, you can read Move a Little, Lose a Lot: New N.E.A.T. Science Reveals How to Be Thinner, Happier, and Smarter. And if you can, walk rather than drive to the library!