"While I haven't heard anyone mention it in a while, [the] HCG diet has to be the worst fad diet I've had someone tell me they were on or told to go on," said Kelly R. Jones MS, RD, CSSD, LDN, to POPSUGAR. Although, any fad diet really isn't good, either. "While on a 500-calorie per-day diet, patients are injected with or take HCG hormone, typically prescribed by 'medical weight loss' clinics."
"There's no better way to hurt your metabolism long term than go on a restrictive diet, limiting yourself to 500 calories per day. Instead, I tell clients to stop calorie counting and help them learn to honor their body's internal hunger and fullness cues," she said. If you're feeding your body when it physiologically needs energy and nutrients, it will run much more effectively than when it's trying to operate on an almost empty gas tank.