We've all read those testimonials about how the "Insanity Workout" craze has transformed people from fat to fit. But while it might seem fantastic to pack 60 minutes worth of exercise into 20 minutes or less, the reality is that it often doesn't equal to long-term results. Amby Burfoot of Runner's World explains why below:
You can't get 60 minutes worth of calorie burn from seven or four minutes worth of exercise.

The math doesn't even come close. Any runners who exchange their four-times-weekly six-mile runs for four seven-minute workouts are going to burn at least 1000 fewer calories per week. Which will lead to a weight-gain of 12+ pounds in a year. Minimum. In one year. Try multiplying that by a couple of years.

And if you gain 12+ pounds a year, there's no way your endurance fitness or health is going to be better than it is today. No way. So what exactly have you gained by following a "scientific 7-minute program"? Beats me, though I think you'll probably have stronger quads, if that turns you on.
So in summary, while shorter workouts can do a lot for your muscles, only a good diet and consistent exercise can provide a sufficient calorie burn that will lead to long-term weight loss. And trust us when we say it's worth the wait.