Any diet will work as long as you're in a moderate calorie deficit — aka "eating fewer calories than you burn," says Laura Hamilton, MA, RD, CSP, LD, of Empower Nutrition. Some people achieve this through a vegetarian or plant-based diet; others do Mediterranean, Paleo, or keto; and some find success with weight-loss plans like Weight Watchers.
Kayley George, MS, RD, LD, owner of The Healthy Weight Loss Dietitians, agrees, saying, "It doesn't matter if you're eating a vegan diet or intermittent fasting; no diet works without a caloric deficit." You can use online calorie-deficit calculators or this calorie-deficit formula to get a rough estimate of your caloric needs. If you want to get more specific, look for a place that offers RMR (resting metabolic rate) testing in your area. It usually costs around $100 to $250 and will tell your more exact caloric needs; it will also indicate what macros (fat, carbs, protein) your body metabolizes best.
If you don't want to bother with numbers and formulas, just be aware of how much you're currently eating. This is the amount needed to maintain your present weight, so if you want to lose pounds, eat about 500 calories fewer, recommends Adrienne Ngai, RD, MSc, CDE. Physical activity can also affect that number, so the more active you are, the less of a calorie deficit you'll need.