Most studies have found positive results of intermittent fasting, including increased insulin sensitivity, reduced levels of oxidative stress, enhanced immune function, and decreased inflammation (1,2). And studies done on those following intermittent fasting for Ramadan showed participants did lose weight, though some of the weight lost included fat free mass (3).On the negative side, studies have also shown that severe calorie restriction can result in higher cardiovascular and cancer mortality (1). It can also result in decreased bone health, especially if the restriction is during adolescence (1). My advice is that though some research shows an increase in overall health with intermittent fasting, the lack of human randomized control trials make it an uncertain territory, and those who wish to practice intermittent fasting should be aware of this lack of evidence and potential health risks.
References:
1. Skaznik-Wikiel ME, Polotsky AJ. The health pros and cons of continuous versus intermittent calorie restriction: More questions than answers. Maturitas. 2014;79:275-278.
2. Faris ME, Kacimi S, Al-Kurd RA, et al. Intermittent fasting during Ramadan attenuates proinflammatory cytokines and immune cells in healthy subjects. Nutr Res. 2012;32:947-955.
3. Norouzy A, Salehi M, Philippou E, et al. Effect of fasting in Ramadan on body composition and nutritional intake: a prospective study. J Hum Nutr Diet. 2013;26:97-104.