The easiest, fastest way to lose weight is not by going to the gym. It's by cutting out carbs completely and living off protein meals, and not burning calories either. You essentially starve yourself of energy so your body starts breaking doen your fat stores, and the protein meals keep you from feeling hungry while this happens.
your body will only go into the starvation state and begin breakdown of adipose tissue if there are no carbohydrate sources available to respire. It's not healthy and it's not a long term plan but its the 'best' way to lose weight.
Ketogenic diets have been shown in studies to be no more effective for fat loss than standard diets. A decent amount of protein in your diet as a part of a balanced diet will lead to no more loss of muscle mass whilst losing weight than a keto diet. No carbs and no dietary fat... RIP hormones.