Overweight? Why Exercise Doesn’t Help Everyone

Image of a man using an elliptical exercise machine.

Exercise Resistance–It’s Real and Makes Losing Weight Much More Difficult

Have you ever felt as if you work out at the gym, jog, and exercise frequently at home but never seem to lose the amount of weight you want? The cause might be high levels of a liver enzyme called selenoprotein-P, according to Dr. Hirofumi Misu and his colleagues, of Kanazawa University in Japan.

Misu and the researchers on his team conducted a study of mice and people that showed the presence of selenoprotein-P seems to be associated with tiring from exercise faster and receiving fewer benefits from it in terms of weight loss than a control group did. This is a condition called exercise resistance.

No, it’s not just in your head.

It is typically recommended that adults should exercise enough to elevate their heart rate for at least 30 minutes, five days a week, or do intense aerobic exercise for 15 minutes a day, five days a week, to stay healthy. This works beautifully for some people; fifteen to twenty percent of others just feel like they’re dying and so exercise less than the recommended amount or forgo exercise entirely. For such people, their bodies might actually be telling them that exercise isn’t a good weight-loss strategy for them.

Exercise resistance and reduced exercise endurance arise from the relationship between selenoprotein-P and AMPK (adenosine monophosphate-activated protein kinase). AMPK is a protein found in all the cells of a person’s body. When a person exercises, AMPK normally generates energy by causing it to be released from ATP (adenosine triphosphate), which allows a person to feel less tired from exercise and to thus exercise longer and to burn more fat from that exercise. But Misu and his colleagues discovered that, when they injected their wild-type mice with selenoprotein-P and then subjected them to a month of scheduled exercise, the mice’s high levels of selenoprotein reduced their bodies’ use of AMPK, which in turn reduced the amount of energy released from ATP in their muscles and consequently reduced the amount of fat burned. The end result was poor benefit from the exercise.

If selenoprotein-P is such a buzz-kill for exercise, what does it do for us? Selenoprotein-P is thought to be an antioxidant that possibly protects us from poisoning by heavy metals, and it might aid in physical and neural development. Biochemists, however, are not entirely certain of its function.

If exercise can’t work for you, how can that situation be changed?

Therein lies the problem. Though researchers have identified selenoprotein-P as a likely barrier to weight loss through exercise, they haven’t yet developed a way to reduce its presence. They hope that their study results will prompt research into creating drugs that can reduce the amount of selenoprotein-P secreted by the liver. This would enable people with exercise resistance to feel less fatigued from exercise and to gain more healthful benefits from it, particularly in the treatment of type 2 diabetes and metabolic syndrome.

Until that time comes, however, you aren’t off the hook. Lay off the carbs and the sugar, drink water, and control your portion sizes.

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