Why weight training increases the thermic effect of food...

Eating food increases your metabolic rate. This increase in metabolism is known as the thermic effect of food.

Researchers from the Department of Kinesiology at the University of Nevada studied the effects of weight training on the thermic effect of food [1].

They measured the metabolic rate of subjects who ate a high-carbohydrate meal containing 660 calories with and without a prior bout of weight training.

Interestingly, there was a higher thermic effect in the exercise trial than in the non-exercise trial.

In fact, the thermic effect of food was 73% greater after the weight training trial than in the control trial. The researchers think part of this response is due to the energy cost of glycogen synthesis.

Glycogen (pronounced gly-ka-jun) is the name given to carbohydrate stored in your body. When you train hard, your glycogen stores are used for energy. If you train hard on a regular basis without replacing the glycogen your body uses, your performance during high-intensity exercise is likely to get worse rather than better.

Research from Washington University School of Medicine also shows that the calories in a meal high in fat or sugar are less likely to be stored as fat if you eat them after exercise [2].

The study shows that 60 minutes of exercise helps to "divert" fat and sugar into muscle, rather than fat tissue. Specifically exercise increases the activity of enzymes responsible for transporting sugar and fat into your muscles.

Studies show that the thermic effect of a meal is also 50% greater in men who train with weights compared with men who are sedentary [3]. In other words, if you train with weights on a regular basis, the effect on your metabolic rate means that you'll burn off more of the calories you eat.

Of course, this doesn't mean that exercise gives you the freedom to eat all you want. The key to losing weight is to burn more calories than you get from your diet. If you simply replace the extra energy you've expended during exercise with additional calories from your diet, then your weight won't change.

References
1. Denzer, C.M., & Young, J.C. (2003). The effect of resistance exercise on the thermic effect of food. International Journal of Sports Nutrition and Exercise Metabolism, 13, 396-402
2. Greiwe, J.S., Holloszy, J.O., & Semenkovich, C.F. (2000). Exercise induces lipoprotein lipase and GLUT-4 protein in muscle independent of adrenergic-receptor signaling. Journal of Applied Physiology, 89, 176-181
3. Thyfault JP, Richmond SR, Carper MJ, Potteiger JA, Hulver MW. (2004). Postprandial metabolism in resistance-trained versus sedentary males. Med Sci Sports Exerc, 36, 709-716