Last updated: October 2026
Magnesium won’t make you lose weight on its own. Two large reviews of around 30 trials found no meaningful change in body weight overall, only small reductions in BMI or waist size in people who were obese, low in magnesium or insulin resistant. Where it may help is indirectly: steadier energy, better sleep routines and less bloating.
Below: what the research actually shows, who might benefit, how magnesium supports a weight-loss plan, the best type and dose, and magnesium with weight-loss injections.
What the research shows
| Review | Trials | Overall result | In subgroups |
|---|---|---|---|
| Askari et al, 2021 | 32 trials, 48 to 450mg a day for 6 to 24 weeks | A tiny drop in BMI (0.21 points, roughly half a kilo for an average adult); no significant change in weight, waist or body fat | Weight and waist fell in people with obesity, low magnesium, insulin resistance or high blood pressure |
| Rafiee et al, 2021 | 28 trials, about 2,000 people | No significant change in weight, BMI, waist or body fat | Waist size fell by about 2cm in people with obesity |
| Veronese et al, 2016 | Trials in people with or at risk of diabetes | Improved fasting blood glucose | Mainly in people with diabetes or low magnesium |
In short: if your magnesium intake is already adequate, a supplement is unlikely to change the scales. If you’re low, correcting it may help your body work normally, which supports everything else you’re doing.
Who might benefit?
- People with a low intake: UK diet surveys show many teenagers, and some adults, get less magnesium than they need. See signs of magnesium deficiency.
- People with insulin resistance or type 2 diabetes: where the trial results were strongest. Talk to your GP before adding supplements to diabetes medication.
- People on a low-calorie diet or eating less because of weight-loss injections, who may get less magnesium from food.
How magnesium can support a weight-loss plan
- Energy: magnesium contributes to normal energy-yielding metabolism and the reduction of tiredness and fatigue, which helps when you’re trying to stay active.
- Exercise: magnesium contributes to normal muscle function.
- Sleep routine: short sleep is linked with weight gain, and many people use magnesium as part of a regular evening wind-down. See magnesium for sleep.
- Bloating and water weight: magnesium contributes to electrolyte balance, and one trial found less premenstrual fluid retention. See magnesium for bloating and magnesium for water retention.
- Constipation: magnesium citrate draws water into the bowel, which can help if a diet change slows things down.
What magnesium doesn’t do
- It doesn’t burn fat or “boost metabolism” beyond normal.
- It doesn’t suppress appetite.
- Any quick drop on the scales from a laxative-type magnesium is water, not fat.
What works is a modest calorie deficit you can keep up, plenty of protein and fibre, regular activity and good sleep. The NHS suggests aiming to lose 0.5 to 1kg a week. See also CBD for weight loss.
Best type of magnesium
| Type | Good for |
|---|---|
| Glycinate (bisglycinate) | Gentle on the stomach; popular in the evening |
| Citrate | Well absorbed; helpful if you’re prone to constipation |
| Oxide | Cheap but less well absorbed; more likely to cause loose stools |
Our Magnesium Glycinate Sleep Complex combines bisglycinate and citrate with glycine, L-theanine and botanicals, giving 148mg of magnesium per serving as a warm evening drink. Compare forms in types of magnesium.
How much to take
The NHS says adults need 300mg (men) or 270mg (women) a day, and that 400mg or less a day from supplements is unlikely to cause harm. Start with food: pumpkin seeds, almonds, leafy greens, beans and wholegrains are all good sources and fit well into a weight-loss diet. If you supplement, 100 to 300mg a day is typical. Speak to your GP first if you have kidney problems.
Magnesium and weight-loss injections
If you’re on Mounjaro or Wegovy, you’re probably eating much less, so your magnesium intake can drop too, and constipation is a common side effect. Magnesium is generally fine alongside these medicines, but check with your prescriber or pharmacist. See best magnesium for Mounjaro.
See also menopause weight gain.
FAQs
Does magnesium help you lose weight?
Not on its own. Reviews of around 30 trials found no meaningful weight change overall, with small benefits only in people who were obese, low in magnesium or insulin resistant.
Which magnesium is best for weight loss?
None causes weight loss. Glycinate is gentle and suits an evening routine; citrate helps if you’re prone to constipation.
Can magnesium help with belly fat?
One review found waist size fell by about 2cm in people with obesity, but not in others. It isn’t a way to target belly fat.
Does magnesium reduce bloating?
It may help some people. Magnesium contributes to electrolyte balance, and one trial found less premenstrual fluid retention after two months.
Can magnesium make you gain weight?
No. Magnesium supplements contain no meaningful calories and aren’t linked with weight gain.
Can I take magnesium with Mounjaro?
Usually yes, and it may help with constipation, but check with your prescriber or pharmacist first.
Sources
- Askari M et al. The effects of magnesium supplementation on obesity measures in adults: a systematic review and dose-response meta-analysis. Crit Rev Food Sci Nutr, 2021.
- Rafiee M et al. The effect of magnesium supplementation on anthropometric indices. Br J Nutr, 2021.
- Veronese N et al. Effect of magnesium supplementation on glucose metabolism in people with or at risk of diabetes. Eur J Clin Nutr, 2016.
- NHS. Vitamins and minerals: magnesium.
- NHS Better Health. Lose weight.
