Mounjaro, Wegovy and Ozempic belong to a class of drugs called GLP-1 analogues. Mounjaro has both GLP-1 and GIP. 

These medications regulate blood sugar and appetite by slowing down the gastric emptying, increasing insulin sensitivity and suppressing glucagon production. As the medication suppresses appetite, it can make maintaining a calorie deficit feel easier for many people. 

Unlike traditional dieting, where hunger eventually drives people to break their calorie deficit, Mounjaro, Wegovy, and Ozempic-like medications can sustain appetite suppression for months or even years, potentially leading to prolonged periods of significant calorie restrictions. 

But why can a prolonged and very-low-calorie deficit be of concern? 

Irrespective of energy deficit or medication, the body tries to adapt eventually, which is one of the main reasons for weight regain. Basal Metabolic Rates fall more than would be expected from just losing muscle mass. Over time, that can make further weight loss harder and increase hunger signals if the medication is discontinued. 

A prolonged very-low-calorie diet also raises the risk of losing lean muscle mass and of nutrient deficiencies. 

Studies show weight loss with Mounjaro, Wegovy, and Ozempic therapies leads to loss of both fat and muscle mass. In some analyses, fat loss was 85% and muscle loss was 15%. 

While staying on Mounjaro, Wegovy and Ozempic-like medication and very-low-calorie diets for a long time, the possible risks include: 

  • Excess muscle loss
  • Bone density loss
  • Micronutrient deficiencies if not having a balanced meal. 
  • Metabolic adaptation that drives weight regain when the deficit eases or medication is discontinued.

Prolonged very-low-caloric restriction can result in micronutrient deficiencies like vitamin B, iron, vitamin D and calcium. These deficiencies can compound the negative effects of muscle loss and metabolic slowdown. 

What can you do to improve?

  • Aim for gradual weight loss and individualised targets. Rapid weight loss and large deficit diets are more likely to cause loss of lean mass and metabolic slowdown. Use the medication as a tool with a supervised plan. 
  • Measure weight, body composition or waist circumference where possible, check bone-relevant risk factors in high-risk groups, and screen for nutrient deficiencies. Adjust caloric targets if excessive lean mass loss is detected. 
  • As metabolic adaptation happens, build a slow transition to maintain energy intake and exercise habits before stopping. 
  • Resistance training is crucial. Up to 50-70% of the muscle mass can be preserved during Mounjaro, Wegovy, and Ozempic-like induced weight loss with resistance training. 
  • Adequate protein intake is essential. It is important to have a balanced and varied diet to cover all micronutrients.   

So, can you maintain a very-low-calorie deficit for too long whilst on Mounjaro, Wegovy, and Ozempic?

While these medications are remarkably safe and effective, extended periods of very-low-caloric restriction beyond 12-18 months may lead to excessive muscle loss, metabolic adaptation, and nutritional deficiencies. 

It is important to work with healthcare professionals to follow:

  • A structured approach that includes a healthy and balanced diet plan
  • Resistance training 
  • Periodic assessment of body composition. 

The goal isn’t just weight loss; it is about achieving and maintaining optimal health while preserving muscle mass and metabolic function.