I’m often asked the question “which should I do first aerobic or anaerobic exercise?”

Personally if I’m trying to reduce fat stores I always perform anaerobic exercise before aerobics, in other words weights before a cardio workout. I believe this to be crucial if consuming an average to high carb (carbohydrate) intake. The reason is simple physiology; weights will always require carbs to supply virtually all the energy needs. A possible exception would be if weights were performed continuously and at very low intensity, although this would become aerobic movements which wouldn’t do much to boost the metabolism anyway!
 

Exercising aerobically first would probably waste the majority of carbohydrate stores in the muscle. If the diet is replenishing glycogen (carb) stores as in a normal carb intake, then I run the risk of using these supplies even when exercising aerobically, after all, carbs are the preferred fuel for working muscle cells. However, if weights are performed first then the majority of the glycogen levels are used up, this forces the cells to utilize more fat to fuel aerobics. In fact it doesn’t do it this way, it’s more of a case that I’m tired from the weights therefore I tend to exercise with a much lower intensity and this is what allows the body to move into fat burning mode. In other words, I just haven’t got that enthusiastic way about me when exercising after doing weights so I have to exercise at lower levels. You know when you’re first starting a workout and energy levels are sharp and positive, well this can sometimes work against fat burning.

Now if I did weights after 30-45 minutes of sweating from a cardio workout I’d probably feel less enthusiastic. Building muscle is such hard work that less than optimal energy levels renders weight training ineffective for stimulating muscle growth, so all I would end up doing is burning more calories. For me, weights have the job of building lean mass to help keep the metabolism high enough to control my weight easily.