FTO and obesity due to melanocortin 4 receptor deficiency: For example, a meta-analysis aiming to determine whether physical activity attenuates the effect of the FTO gene on obesity risk was forced to dichotomise physical activity (active or inactive) across the multitude of exposure measures [6]; while this was sufficient to confirm the existence of an interaction, it was not possible to determine what dose of activity was necessary to protect against the deleterious FTO variant.