Metabolism

Adiposity is characterized by the lowest basal metabolic rate (BMR), hence obese people are burdened with slowest homeostasis.
Aiming at higher basal metabolic rates (BMR) helps melting fat stores and obtaining a lean physique, which would accelerate in turn metabolism also.
Thus, all functions become faster, including the immune system.
The organism becomes healthier, more infections-resistant, epidemics-resilient even, and all sorts of aggressions-unyielding.
Body strength is an essential part of it as well.
Cold baths increase amount of brown body fat, and thus accelerate metabolic rate. (Beware of thermic shock!)
Exercise is best in the morning, on an empty stomach, which helps regulating corticosteroid secretion.