Many people making huge mistake in doing only cardio for weight loss. That way they are killing long term metabolism and will gain even more fat. In order to activate metabolism and increase the metabolic rate, strength training is needed for the increase of lean muscle mass and to optimize the neuro-mechanism of the body. – Joe DiAngelo, PhD

In the first place people gain weight due to the rapid decrease of the metabolic rate caused by the inactivity. Inactivity leads with the age to the loss of the lean muscle man which represent the lower metabolic rate due to the loss of the muscle mass.

Muscle is the fat burning machine of the human organism and loss of the lean muscle mass cause man to gain weight and rapidly increase the body fat percentage that leads to the imbalance in Neural Mechanisms.
The imbalance in neural mechanism of the human body leads to the mixture of hormones within a body and negative hormonal profile that cause man to get out of the normal production of mechanical bio processes within a body.
Imbalance in hormonal profile is caused by the loss of muscle cells. Thus we as humans gain the fat and all is caused by inactivity and decrease of muscle cells.

Scientific evidence shows us the real picture of the metabolic slowdown. Only way to fight the ever growing increase of fat cells is with increase of the muscle mass.
Human body needs to balance the increase of the fat cells with increase of the muscle cells .
And the most effective and best way to gain lean muscle mass is weight and strength training and not an aerobic exercises like spinning, dancing, all kinds of jumping fitness trends of today.
Those cardio classes are just designed for commercial gain without any scientific research nor evidence for the people who have no knowledge of bio mechanics of the human body and processes within that lead to the fat loss. Those classes are often designed from uneducated people who do not even know the bio mechanics of the human body.
Are you going still to apply cardio exercises for your weight loss strategy that you know the truth? Are you still hoping to lose weight without getting involved in strength training? Or you will still stay ignorant and one more year lost in getting involved in ineffective programs hoping that something will change?
And next year will be some new fitness fad, some new zomba bomba dance, some new hanging from the rope, some new cycling class, some new never ending celebrity endorsed fitness gimmick and the life gets spent without results you deserve.
Do you remember the fitness trends of few years ago. Now they are history and nobody mentions it anymore.
Sometimes people portray something as fun and effective exercise just to involve you, but on the end you will yourself experience how effective and fun it really was for you. I do not see anything fun and effective in spending so many hours in ineffective workout programs without yielding results.

You might lost some muscle cells but do not allow yourself to lose brain cells too. You know better.