Fat Oxidation: Do we have it all wrong? by Jerry Brainum 2/22

Summary

 

 

 

 

A few recent articles have played down the benefits of exercise for promoting body fat loss. You've probably heard that a pound of fat contains 3,500 calories and that a typical workout with weights burns only about 300 calories, with another 200 or so added if you also include some aerobics after the weight workout. The exercise naysayers like to say that such comparatively meager calorie burning means that exercise somehow isn't effective for promoting any significant fat loss. But that doesn't make sense because exercise works in a cumulative manner; that is, those calories burned during training add up and make definite inroads towards body fat reduction.  Another frequent critique of exercise in relation to fat loss is that exercise, because it does burn calories, causes you to be hungry after the workout, and thus seek to replace all the calories that you burned during exercise.  I've always found such statements curious since I have always had a depressed appetite following training that lasts for about 3 hours. But more recent studies have clarified the appetite/exercise debate. These studies have found that only excessive exercise will significantly increase appetite. Excessive could be defined as training more than 3 hours in a single workout or doing 2 consecutive hours of aerobics following a weight workout. Normal degrees of training, such as an hour or two in the gym if anything, tend to decrease appetite.

One thing that cannot be denied about exercise and fat loss is that fat is oxidized in the presence of oxygen, and the more oxygen that is present, the greater the rate of fat oxidation. This applies to physical activity since at rest the body prefers to oxidize fat as a fuel source in order to preserve limited glycogen stores in the body. Of course, the amount of fat oxidized while at rest is minuscule. This is self-evident since if just sitting around burned appreciable amounts of stored fat, obesity wouldn't exist. Aerobics or endurance activity is thought to burn more fat because it features a higher oxygen intake.  Studies that have directly compared resistance training to aerobic exercise have found that aerobics usually proves superior for fat oxidation during exercise, but not so much following exercise. The reason for that is that aerobics, with the exception of high-intensity interval training or HIIT, only raises the resting metabolic rate during the exercise. As soon as the exercise ends, the metabolic rate returns to baseline levels. But weight-training causes something called post-exercise increased oxygen expenditure, which is a fancy way of saying that the metabolism stays higher for hours following a weight workout because of the recovery process involved after resistance training. Aspects of recovery such as muscle protein synthesis, which is the cornerstone of increased muscle mass gains, are highly energy-intensive and uses up calories in . . .