If you are adolescent, pregnant, breastfeeding, have a medical condition, or want to lose more than 20% of your weight, then talk about your weight loss plans with your doctor or dietitian. SlimFast meals are not designed to be your only food - add a balanced nutritious meal (600kcal for women and 800kcal for men) and healthy snacks every day. Can only help weight loss as part of a calorie controlled diet and an active lifestyle.