If you have a lot of weight to lose, have a stubborn weight that is difficult to budge, or have hit a weight loss plateau on the keto diet and want rapid weight loss, it may be worth trying the PSMF diet. Obese patients need to be medically supervised on very low-calorie diets. Rapid weight loss may affect their blood pressure, and blood sugar control, and because medical PSMF is longer than a crash diet, they need to be monitored for any nutritional deficiencies.