Often times, many competitors and fitness models will gain a drastic amount of weight a few days after their show.  Maybe one is not a competitor, but they dieted in preparation for a vacation or wedding.  The weight comes back after the diet is over, and it is even harder to lose.   Women have shown to gain 20 to 25 lb. right after.

The single factor that determines the fat loss in the body is the metabolic rate (metabolism).   It is not caloric deficit or doing endless hours of running on the treadmill.  Without metabolism, one is dead in the water. Think of this scenario:

One avoids carbs and fats all day.  They finish each day with about a 500-calorie deficit.  In fact, they did two hours of cardio on this plan.  However, with no metabolism or metabolic rate, one cannot and will not lose body fat.

What damages the metabolic rate? 

1. Constant and steady low intensity cardio (walking on the treadmill, stairmaster, elliptical etc.).  This is where one can lose the fat burning component of steady state cardio quickly.
2. Restrict calories or not having enough fats and good carbs in the diet.
3. Eating 1200 calories a day but burn 500-1000 in workouts
4. Complete each day at a caloric deficit.  (Carb cycling is very important for this reason!)

 
What builds the metabolic rate?

1. Lifting weights, building muscle and high intensity lifting.  For females, it is recommended to lift hard and heavy as often as possible. By adding muscle, this adds to the metabolic rate.  In fact, the more muscle one has, the more calories the body will burn.
2. High Intensity Interval Training “HIIT” is the only type of cardio that the body does not adapt.  It encourages the metabolic rate and fat burning component.
3. Eating enough quality calories is so important.  To lose weight, one needs to eat.  To build muscle, one needs to eat.  Starvation diets will lose the fat loss ability.