Ever wondered why there are so many conflicting expert opinions regarding the ultimate weight-loss diet? Perhaps it is because a universal diet doesn't exist but that it is down to your genetic constitution. Nutrient intake and physical activity are essential factors affecting body weight, body composition, energy metabolism, and energy utilization. However, not everyone responds to the same exercise and diet regimes n the same way. Indeed, a large part of our ability to gain or lose weight is down to our genes, which are involved in the susceptibility to gaining or losing weight in response to a given diet, to appetite, lipid over-absorption, and more.