Intermittent fasting, also known as intermittent energy restriction, is an umbrella term for various meal timing schedules that cycle between voluntary fasting (or reduced calories intake) and non-fasting over a given period. Three methods of intermittent fasting are alternate-day fasting, periodic fasting, and daily time-restricted feeding. intermittent fasting is also regarded as a fad. The science concerning intermittent fasting is contested. The American Heart Association (AHA) states that intermittent fasting may produce weight loss, reduce insulin resistance, and lower the risk of cardiometabolic diseases, although its long-term sustainability is unknown. A 2019 review concluded that in humans, intermittent-fasting interventions may help with obesity, insulin resistance, dyslipidemia, hypertension, and inflammation.