Successful fat loss is achieved through the creation of a negative energy balance. One needs to burn more calories than they take in through food.
How the body burns and utilizes calories daily is made up of the following:
- Resting Metabolic Rate (RMR) is the calories your body burns at rest.
- Activity Energy Expenditure (AEE) is the calories burned during exercise
- Non-Exercise Activity Thermogenesis (NEAT) is the calories burned from all activities other than exercise over the course of the day (digestion, thermal regulation, brain cognition, other internal causes).
Aerobic exercise (long duration, low intensity) has typically been recommended because, at moderate intensities, it has the power to increase activity energy expenditure (AEE) more than weight training due to the fact that weight training is intermittent and includes rest periods.
However, the conventional way of doing 45-60 mins/day of cardio leads to poor returns due to the fact that people lose a lot of muscle mass in addition to any fat loss, and their resting metabolic rate drops. They burn fewer and fewer calories, and end up actually increasing body fat over the long run.
Weight training helps build muscle and lean muscle mass is responsible for substantially increasing the other two factors, RMR and NEAT, so that you burn more total calories over the course of the day, everyday. Would I rather be burning fat only when I'm working out or would I prefer my body to continue to burn fat even when I'm not training? I think that's an easy question to answer...
Training with weights and shifting the focus towards strength training is an essential part of any successful fat loss program because it increases your total energy expenditure in quite a few ways.
Not only does building muscle increase your resting metabolic rate, but intense exercise (like strength training) increases levels of epinephrine and norepinephrine. These hormones result in an increase in carbohydrate and fat burning, which also plays a role in raising the resting metabolic rate.
Intense exercise and strength training also leads the body to burn energy at an accelerated rate around the clock after exercise -called EPOC for "excess post-exercise oxygen consumption". Basically, the body requires extra oxygen in order to perform recovery processes including restoring muscle energy stores and repairing damaged tissue.
Weight training also restores insulin sensitivity. Insulin resistance occurs when the cells in your body don't readily bind to insulin, which means that blood sugar is not effectively used by the body. When this happens, the body stores more of the food you eat as fat and energy levels will be reduced because your muscle cells aren't getting the fuel they need. High insulin also causes inflammation which leads to accelerated aging and disease.
Weight training can prevent all of this misery and enable body fat loss by restoring the sensitivity of your cells to insulin. Anaerobic forms of exercise (like strength training or HIIT) are some of the best ways to force your cells to become more sensitive to insulin, which allows the body to burn blood sugar for energy.