Intermittent fasting (IF) diets are increasingly popular as a dietary tool to improve health and reduce body weight, although only a handful of trials have been conducted in humans to date. In lean animals, intermittent fasting clearly increases lifespan and reduces chronic disease risk, even without significant weight loss. These findings suggest that periodic energy deprivation, rather than weight loss per se, can provide the impetus to improve metabolic health. However, it is not clear whether similar results will be noted in obese mice. Although, metabolic health parameters are improved following time restricted feeding in obese animals. We have recently conducted an 8-week randomised controlled feeding trial in women who are overweight and obese, to test whether fasting is as effective as daily dietary restriction (DR) to reduce body weight, improve insulin sensitivity and reduce cardiovascular risk, and importantly we have tested whether weight loss is necessary for these benefits. Results from this trial will be presented, and this seminar will also discuss the potential mechanism/s underlying the improved health benefits of fasting.