Are you eating too little on Mounjaro?

Jump to: Signs you’re not eating enough | Why eating enough matters | Working out your needs | Making it easier to eat | When to get help | Frequently asked questions | Take home message

If you’re consistently losing more than 1kg (2 pounds) per week on Mounjaro, you might not be eating enough to support healthy weight loss.

Research from the SURMOUNT trials shows that participants on Mounjaro lost an average of 0.4-0.6kg per week¹.

While Mounjaro (tirzepatide) does reduce your appetite, about 5-10% of users find their hunger lowers to such an extent that they struggle to eat enough². This can cause problems, including muscle loss, nutrient deficiencies, and gallstones.

A study of 101 postmenopausal women found that those who severely restricted their calories (eating 65-75% less than normal) lost 2.5 times more bone density in their hips compared to those who ate more moderately (25-35% less than normal)³. The severely restricted group also lost significantly more muscle, despite both groups losing similar amounts of weight overall.

Understanding how to eat enough while on Mounjaro is important to ensure losing weight doesn’t contribute to other health problems down the line.

Signs you’re not eating enough on Mounjaro

Your body will tell you when it’s not getting what it needs:

Physical warning signs:

• Feeling exhausted even after a good night’s sleep
• Being cold all the time, especially your hands and feet
• Hair falling out more than usual
• Nails breaking easily or growing slowly
• Constipation getting worse
• Feeling dizzy when you stand up
• More headaches than normal

Mental and emotional changes:

• Can’t concentrate properly or feel ‘foggy’
• Snapping at people more than usual
• Feeling anxious about food
• Can’t stop thinking about food (even though you’re not hungry)
• Trouble sleeping

Your ability to do everyday activities declines:

• Feeling weaker when doing everyday things
• Taking longer to recover after exercise
• Low libido
• Periods are becoming irregular or stopping

Why eating enough matters on Mounjaro

What happens when you don’t eat enough

When you eat too little, your body goes into survival mode:

1. Your metabolism slows down: It can drop by 15-30% when you’re eating too little⁵
2. You lose muscle: Your body starts breaking down muscle and other lean tissues for energy
3. Your hormones become unbalanced: Especially thyroid hormones, which impact how well our body uses and stores energy
4. Risk of nutrient deficiencies: Essential vitamins and minerals get depleted

The risk of gallstones

Losing weight too quickly is one of the main causes of gallstones. Research shows that losing more than 1.5kg per week increases your gallstone risk by 20-25%⁶. This is especially worrying for Mounjaro users, since the medication already has a small risk of gallbladder issues.

Maintaining muscle mass

Research shows that eating enough protein (1.2-1.6g per kg of body weight) while creating a moderate calorie deficit helps you keep much more muscle than severely restricting calories⁷.

Making it easier to eat when you’re not hungry

1. Eat 3 balanced meals a day and include snacks if needed

As Mounjaro can lower your hunger to the point where you might need feel hunger to trigger you to eat, it’s essential to maintain a regular eating schedule.

• Set reminders on your phone for meals
• Eat every 3-4 hours, whether you feel like it or not
• Have breakfast within 2 hours of waking up
• Plan for 3 meals and 1-2 snacks each day

2. Pick proteins that go down easily

Some proteins are easier to eat and digest when you have no appetite:

Easiest options:

• Greek yoghurt (20g protein per 200g)
• Cottage cheese (25g per 225g)
• Scrambled eggs (13g per 2 eggs)
• White fish like cod (20g per 100g)
• Protein powder in smoothies (20-30g per scoop)

Not too difficult:

• Mince dishes like bolognese
• Slow-cooked chicken that falls apart
• Tinned fish in oil
• Silken tofu (10g per 125g)

Save these for when you feel better:

• Grilled steak
• Plain chicken breast
• Tempeh
• Pork and lamb cuts

3. How to add more energy to your meals

Adding some fat from whole foods that are easy to digest can maintain adequate energy intake without adding too much volume:

Each adds 100-150 calories:

• 1 tablespoon nut butter
• Quarter of an avocado
• Tablespoon of olive oil or knob of butter
• A handful of grated cheese
• 2 tablespoons double cream
• Small handful of nuts

4. When you can’t face solid food

You can try liquid-based meals with added protein and energy:

Easy smoothie:

• 200ml whole milk
• 100g Greek yoghurt
• Banana
• 100g frozen berries
• 1 scoop protein powder
• 1 tablespoon almond butter

Other liquid options:

• Full-fat milk or fortified plant milk
• Bone broth with cream stirred in
• Soup with 3-4 boiled eggs
• Kefir

When to get help

Ring your doctor straight away if:

Urgent signs:

• You’re losing more than 1kg a week for 3 weeks or more
• You can’t manage to eat 1,000 calories a day
• You’re dehydrated (dark urine, feeling dizzy)
• You’re so tired you can’t do normal things
• You have chest pain, or your heart’s racing
• You can’t stop being sick

See your doctor within a week if:

• Your hair’s falling out noticeably
• Your periods have changed or stopped
• You’re feeling depressed or very moody
• You’re constipated despite trying remedies
• You’re developing fears about eating

Your prescriber may need to adjust your Mounjaro dose or provide additional support.

Frequently asked questions

How many calories should I eat while taking Mounjaro?

Most people need between 1,500-2000 calories daily while losing weight on Mounjaro. It depends on your size, level of activity, and metabolism.

What happens if I only eat 500-800 calories a day on Mounjaro?

Eating this little can cause serious problems including gallstones, losing lots of muscle, hair falling out, nutrient deficiencies, and your metabolism slowing down.

Studies show that this can reduce your metabolic rate by up to 30%, making it particularly challenging to maintain weight loss later.

Can eating too little on Mounjaro cause hair loss?

Yes, not eating enough is a common cause of temporary hair loss (called telogen effluvium). It usually shows up 2-4 months after you start undereating. Making sure you get enough energy and protein should help to prevent this.

Should I force myself to eat if I’m not hungry on Mounjaro?

You don’t need to force down big meals, but you should eat small amounts regularly throughout the day, even without hunger.

Think of it like taking medicine – your body needs the nutrition whether you want it or not. Focus on nutritious foods in smaller portions.

Will eating more slow down my weight loss on Mounjaro?

Eating enough (usually 500-750 calories below what you burn) actually helps you lose weight more sustainably. While eating very little might cause you to lose weight faster at first, you’ll lose more muscle, slow your metabolism, and be more likely to regain the weight.

Can I use meal replacement shakes on Mounjaro?

Generally, we don’t recommend using meal replacement shakes, as they often contain added preservatives, sweeteners, and other chemicals with unknown health effects.

They can be used occasionally if you’re having trouble consuming whole foods, but we’d recommend prioritising making whole food meals easier to digest, like making more soups and one-pot meals where the meat and vegetables are cooked down so they’re softer and easier to eat.

How do I know if my appetite suppression is too severe?

Get medical advice if you can’t eat at least 1,000 calories daily, feel sick at the thought of food, or get anxious about eating. You might need your dose adjusted.

Take home message

While Mounjaro effectively reduces appetite, you still need to eat enough to stay healthy and lose weight sustainably.

Aim to consume 500-750 fewer calories than you burn each day, ensuring you get enough protein and nutrients. If you’re losing more than 0.9kg weekly or struggling to eat, talk to your doctor about adjusting your dose.

Remember: losing weight isn’t about starving yourself. It’s about feeding your body properly while consuming a bit less than you burn, thereby maintaining your muscles, metabolism, and overall health.

References

1. Jastreboff AM, et al. (2022). Tirzepatide Once Weekly for the Treatment of Obesity. New England Journal of Medicine, 387(3), 205-216.
2. Wilding JPH, et al. (2022). Weight regain and cardiometabolic effects after withdrawal of semaglutide. Diabetes, Obesity and Metabolism, 24(8), 1553-1564.
3. Seimon RV, et al. (2019). Effect of Weight Loss via Severe vs Moderate Energy Restriction on Lean Mass and Body Composition Among Postmenopausal Women With Obesity: The TEMPO Diet Randomized Clinical Trial. JAMA Network Open, 2(10), e1913733.
4. National Institute for Health and Care Excellence. (2023). Obesity: identification, assessment and management. NICE Clinical Guideline 189.
5. Greenway FL. (2015). Physiological adaptations to weight loss and factors favouring weight regain. International Journal of Obesity, 39(8), 1188-1196.
6. Weinsier RL, Ullmann DO. (1993). Gallstone formation and weight loss. Obesity Research, 1(1), 51-56.
7. Cava E, et al. (2017). Preserving Healthy Muscle during Weight Loss. Advances in Nutrition, 8(3), 511-519.