Many Nutrisystem plans are very restrictive and may not provide enough calories for some people, which could increase the risk of nutrient deficiencies and other adverse effects (15).
Losing weight too quickly — regardless of which diet program you use — can slow your metabolism and increase the risk of certain health issues, including gallstones (10, 16).
For this reason, it's always best to consult a doctor or dietitian before starting any weight loss program