Successful weight loss requires a daily caloric deficit (combined decreased food intake and caloric expenditure) of 500 calories per day. People have trouble sustaining this, so they usually gain back any weight they lose. Diet gimmicks, such as liquid weight loss meals, are effective tools for weight loss. A study from the University of Illinois at Chicago led by Krista Varady found that fasting every other day (consuming 25 percent of daily calorie needs) caused weight loss in obese and lean people. After twelve weeks, people lost more than eleven pounds and decreased fat mass by nearly eight pounds without changing lean mass. They also reduced heart disease risk factors such as triglycerides, LDL cholesterol (bad cholesterol), and C-reactive protein (measure of inflammation). However, a larger and more recent six-month study on 100 people found that alternate day fasting did not produce greater adherence, weight loss, or protection against heart disease than daily caloric restriction. Consistent weight loss requires consuming fewer calories than you burn. No single method works best for everyone.
(Journal American Medical Association, published online May 1, 2018; Nutrition Journal 12: 146, 2013)