Low-calorie diets are good for losing weight, but physical activity is more effective at maintaining a target weight. https://www.mayoclinic.com/health/weight-loss/AN01619
Very-low-carb diets result in higher metabolism but might also increase stress and risk of heart problems. Low glycemic index diets might be healthier for long-term weight maintenance. http://www.nih.gov/researchmatters/july2012/07162012weight.h...