Question

describe the human body response at the cell level to perceived starvation threats as when a person is dieting or ill, tell why this was needed in human beings in the past. Is this help or hindrance in modern weight loss diets?

Answer 1

The human body responds to starvation threats by mobilizing the storage fat in adipocytes (fat cells) out of the cell to make energy. The fat cells shrink, but they are still there. The body sends the brain a signal that we need to eat more and our hunger signals increase. The body also lowers our Resting Metabolic Rate, so that we can survive on lower calorie intake. This evolved in humans as a survival mechanism in times of poor or variable food supplies, as the people who carried more body fat were the ones most likely to survive a famine and also they could survive on smaller amounts of food. This is a hindrance to modern weight loss methods, especially to maintain long term weight loss. Once a person returns to normal food intake the body quickly refills the fat cells as they are already there. The lower metabolic rate causes a calorie intake that once maintained weight to cause weight gain.

Answer 2

Briefly, the human body response to starvation at a cellular level results in a reduced metabolic rate and a switching of 'food supply' for various cells. Glucose is a primary cellular food source used by all cells in the body. During starvation with no additional glucose available to the body, glycogen stores (glucose stores) are consumed and then the body turns to consuming fat stores and muscle tissue (protein) to fuel it's cells. This means fat and muscle tissue is broken down during starvation periods. In the past during long periods of starvation, the ability for the body to survive without food input for weeks was necessary for survival. Today, whilst starvation no doubt yields weight loss results, it comes at a price. During starvation muscle tissue is invariably lost as the body needs glucose to power the heart and brain cells, which rely almost exclusively on glucose (which cannot be liberated from the break down of fats). As the body loses muscle tissue, it also loses the ability to burn as much energy because muscles are a key energy user. The body also loses strength in general. It therefore is a hindrance to starve for modern weight loss objectives and a better option is high level of exercise with reduced calorific food intake. This will maintain muscle tissue and favour fat loss.