Randomised trials comparing popular diets head to head typically find only modest average differences in weight loss between them, yet within any single trial, individual responses vary enormously, some participants losing significant weight on a given diet while others on the very same diet lose little or even gain weight. This suggests that a diet's average performance across a population may say little about how well it will suit any particular person.

Which among the following is the most logical and rational inference that can be made from the above passage?