One of the the most pervasive myths around women and fitness is that women need to do a lot of low intensity cardio (aerobics) to be lean and improve body composition. The truth is that performing excess cardio will only make you fatter in the long run.

One of the reasons is that too much aerobic exercise increases stress hormones, which leads to overeating, and down regulates growth hormone, the hormone that signals your body to build muscle and burn fat.

High volume aerobic training also converts your fast twitch muscle fibers into intermediate and slow twitch muscle fibers, and decreases your total muscle mass, which slows down your metabolic rate, so you expend less energy (calories), at rest.

The best way to burn fat is high intensity interval training (HIIT), especially when combined with high intensity (low rep) weight training and proper nutrition. Interval training burns more calories than aerobics and elevates your metabolism significantly more after you finish exercising, while your metabolic rate recovers back to pre-exercise levels.

In a recent study, researchers Trapp & Boutcher put 45 overweight women through a 15 week study where one group was a control, one group did intervals (20 minutes of eight seconds of sprinting on a bike followed by 12 seconds of recovery at a slower pace), and one group did 40 minutes of aerobics.

The researchers found that the interval group lost an average of 2.5kg in the 15 weeks and the steady-state group gained .5kg. In other words, the interval group lost three times as much fat doing half as much exercise.

These results really speak for themselves!