Dr. Mercola recently published this article on his site. He starts by discussing new research regarding meal frequency and metabolism. The general sentiment of his article is that eating more often does not increase metabolism, but eating more frequently might help some people control hunger and, in turn, lead to weight loss.
Great! I agree.
Here’s where we part ways. Dr. Mercola goes on to state that exercise has been proven to raise metabolic rate and he continues by saying each pound of muscle burns 50-70 calories/day while fat burns nothing!
We discuss the science regarding his latter claim in our previous post, Muscle Metabolism Myth
As for exercise raising the metabolism, Stiegler and Cunliffe wrote…
On combined aerobic and resistance training:
“However, considerable controversy remains about the degree of the influence of exercise on RMR [resting metabolic rate].”
On aerobic training alone:
“The impact of exercise intensity on FFM [fat free mass] and RMR [resting metabolic rate] warrants further evaluation.”
On exercise in general:
“Nonetheless, with regard to RMR [resting metabolic rate], the literature to date is still inconclusive, as exercise training has also been associated with reductions in RMR [resting metabolic rate].”
This hardly supports Dr. Mercola’s view that exercise raises the metabolism. Intensity and duration of exercise seem to be tied to its ability to affect metabolism, and most common exercisers are probably not reaching a level of either that would elicit a noticeable metabolism boost. When you take into consideration the other effects being studied, like an adaptive decrease in thermogenesis due to caloric restriction (metabolism slowing down when you eat less) and a reduction in spontaneous physical activity after exercise, the picture becomes less clear.
Our understanding of the calories in calories out equation is minimal, except for the basics. We know that if we’re not losing weight, then our calories in equal our calories out, plain and simple. Many things, it seems, can affect the ‘calories out’ side of the equation but people overlook the most obvious and most easily controllable variables in pursuit of other, less impactful ones.
Focus on what we do know. Eat a calorie-restricted, nutrient-dense diet. Use resistance training to maintain muscle. Perform other enjoyable forms of exercise for overall health.
Stiegler P, Cunliffe A. The role of diet and exercise for the maintenance of fat-free mass and resting metabolic rate during weight loss. Sports Medicine 2006; 36(3):239-262.