- Health advice
- 5 min read
- Mar 25, 2026
Last updated: 8 October 2026
Magnesium on its own does not cause meaningful weight loss, and reviews of clinical trials found little or no change in body weight for most people. Small benefits appeared mainly in people who were low in magnesium, living with obesity or struggling with blood sugar control, so it is best seen as support alongside diet, sleep and activity.
How this guide was put together: Reviewed by Yurie Sato (BHSc Naturopathy) against current research, including NHMRC Nutrient Reference Values, TGA guidance, Australian Bureau of Statistics nutrition survey data, healthdirect, NIH Office of Dietary Supplements fact sheets and peer-reviewed systematic reviews and meta-analyses, and updated as new evidence emerges. See our editorial policy or meet our practitioners.
Key points
- Two large reviews of magnesium trials found little or no effect on body weight, waist size or body fat for most people.
- In the 2023 national nutrition survey, 42% of Australian men and 30% of women aged 18 and over got less magnesium from food than the estimated average requirement.
- Australian guidelines set an upper limit of 350 mg a day from supplements for anyone aged 9 and over.
- Compare products by elemental magnesium, the amount of magnesium itself, not the weight of the whole compound.
Does magnesium help you lose weight?
Not by much, based on the best evidence available. That evidence comes from meta-analyses, which pool the results of many clinical trials to get a clearer answer.
A 2021 meta-analysis looked at 32 trials where people took 48 to 450 mg of magnesium a day for 6 to 24 weeks. Compared with a placebo (a dummy pill), magnesium did not change body weight, waist size or body fat overall.
Body mass index (BMI), a measure of weight for height, did fall by 0.21 points. For someone 170 cm tall, that works out to roughly 0.6 kg.
That small change came mainly from people who were low in magnesium, living with obesity or had problems with insulin at the start. Results also varied a lot from trial to trial.
A second 2021 meta-analysis of 28 trials and 2,013 people found no significant change in weight, BMI or body fat. Its authors said more high-quality studies are needed.
So magnesium is not a fat burner. Where it may help is in filling a gap if your diet is short on magnesium.
What does magnesium do in your body?
Magnesium is a mineral your body needs for healthy muscles, nerves, bones and blood sugar levels. It also helps your body make protein, bone and DNA.
It helps more than 300 enzymes do their job. Enzymes are proteins that speed up reactions in the body, including the ones that make energy from food.
Blood sugar and insulin
Insulin is the hormone that moves sugar from your blood into your cells. A 2021 review of 25 trials found magnesium may improve blood sugar and how well insulin works in people at higher risk of blood sugar problems.
Many of those trials were small and short, and results varied widely. This is why magnesium is best seen as support, not a fix.
Sleep and stress
A review of three small trials in older adults with sleep problems found magnesium helped them fall asleep about 17 minutes faster. The reviewers rated this evidence as low to very low quality.
The evidence for stress is weaker again. A systematic review found some signs of benefit for anxiety in people prone to it, but rated the quality of that evidence as poor.
Muscles and exercise
Because magnesium supports normal muscle function, you will find it in some of our muscle recovery supplements. If you are training more as part of a weight loss plan, make sure your diet covers your magnesium needs.
Does magnesium help you lose belly fat?
There is no strong evidence that magnesium targets belly fat. In the review of 28 trials, waist size did not change overall.
In people with a BMI over 30, waist size dropped by about 2 cm on average. This was one subgroup result, so it needs to be confirmed in larger, better trials.
What about magnesium oil for belly fat?
Some people rub magnesium oil or spray on their stomach. A 2017 review found the idea that magnesium is absorbed well through the skin is not supported by the science.
That means magnesium oil is not a way to reduce belly fat. If you need more magnesium, food and oral supplements are the better-studied options.
Can magnesium curb your appetite or help you lose water weight?
We could not find good-quality trials showing that magnesium supplements reduce appetite or cravings. Low magnesium can cause a loss of appetite, so the link is not simple.
High doses of magnesium can cause diarrhoea, nausea and stomach cramps. Any drop on the scales from this is fluid, not fat, and it is a sign the dose is too high.
Are you getting enough magnesium?
Many Australians are not. In the 2023 national nutrition survey, 42% of men and 30% of women aged 18 and over got less magnesium from food and drinks than the estimated average requirement, a level that meets the needs of about half of healthy people.
Some groups fell short more often, including 44% of girls aged 12 to 17 and half of men aged 75 and over. The figures for women exclude those who were pregnant or breastfeeding.
Foods high in magnesium include green leafy vegetables, legumes, nuts and seeds, and wholegrains. The table shows how much some common foods provide.
| Food | Serve | Magnesium (mg) |
|---|---|---|
| Pumpkin seeds, roasted | 28 g | 156 |
| Chia seeds | 28 g | 111 |
| Almonds, dry roasted | 28 g | 80 |
| Spinach, boiled | ½ cup | 78 |
| Cashews, dry roasted | 28 g | 74 |
| Soy milk | 1 cup (about 240 mL) | 61 |
| Black beans, cooked | ½ cup | 60 |
| Brown rice, cooked | ½ cup | 42 |
| Banana | 1 medium | 32 |
Figures are from the US National Institutes of Health. Amounts in Australian products can differ, so check the nutrition panel.
How much magnesium should I take for weight loss?
There is no proven magnesium dose for weight loss. The trials used anywhere from 48 to 450 mg a day, with little effect on weight for most people.
Australian guidelines set a Recommended Dietary Intake (RDI), which is how much most people need each day from food, drinks and supplements combined. They also set an upper limit for supplements only, because magnesium from food has not been shown to cause harm.
| Group | RDI (mg a day) | Upper limit from supplements (mg a day) |
|---|---|---|
| Children 1 to 3 years | 80 | 65 |
| Children 4 to 8 years | 130 | 110 |
| Children 9 to 13 years | 240 | 350 |
| Boys 14 to 18 years | 410 | 350 |
| Girls 14 to 18 years | 360 | 350 |
| Men 19 to 30 years | 400 | 350 |
| Men 31 years and over | 420 | 350 |
| Women 19 to 30 years | 310 | 350 |
| Women 31 years and over | 320 | 350 |
| Pregnancy | 350 to 400, depending on age | 350 |
| Breastfeeding | 310 to 360, depending on age | 350 |
Source: NHMRC Nutrient Reference Values for Australia and New Zealand.
Women have lower magnesium needs than men, so a smaller dose may be enough. You can compare options in our magnesium for women range.
Check the elemental magnesium
Elemental magnesium is the amount of magnesium itself, not the weight of the whole compound it comes in. For example, one scoop of Ethical Nutrients Mega Magnesium contains 2.3 g of magnesium glycinate, which provides 300 mg of elemental magnesium.
Some product labels suggest more than 350 mg a day. That can suit some people under a practitioner’s care, so check with one before going above the limit.
Which magnesium is best for weight loss?
No form of magnesium has been shown to cause weight loss, including magnesium glycinate. The form mainly affects how well it is absorbed and how your gut handles it.
| Form | What to know |
|---|---|
| Glycinate (bisglycinate) | Magnesium bound to the amino acid glycine. It is not on the US National Institutes of Health list of forms most often linked to diarrhoea. We found no trials testing it for weight loss on its own. |
| Amino acid chelate | Magnesium bound to amino acids. Glycinate is one type, and some blends use several. |
| Citrate | Absorbed more completely than oxide in small studies. |
| Aspartate | Absorbed more completely than oxide in small studies. |
| Oxide | Absorbed less completely than citrate, aspartate or chloride. It is one of the forms most often linked to diarrhoea. |
| Chloride | Used in oils, flakes and some tablets. Taken by mouth it is absorbed better than oxide, but it is also linked to diarrhoea at high doses. |
You can compare forms and strengths across our magnesium supplement range. A practitioner can help you match the form to your needs and any medicines you take.
How do popular magnesium supplements compare?
None of these is a weight loss product. The table shows what each label states, so you can compare elemental magnesium and extra ingredients.
| Product | Elemental magnesium | Magnesium forms | Also contains | Access |
|---|---|---|---|---|
| Ethical Nutrients Mega Magnesium Raspberry Powder | 300 mg per 8.7 g scoop | Glycinate blend | Taurine 3 g, vitamin C, calcium, potassium, vitamin B6 (pyridoxine hydrochloride 50 mg) | Over the counter |
| Fusion Health Magnesium Advanced | 200 mg per tablet | Glycinate, citrate, amino acid chelate, aspartate | No other active ingredients | Over the counter |
| BioCeuticals Ultra Muscleze P5P | 150 mg per tablet | Amino acid chelate including glycinate | Vitamin B6 34.2 mg per tablet (as P5P) | Practitioner-only, after a consultation |
| BioCeuticals Ultra Muscleze Powder | 280.2 mg per 6 g serve | Amino acid chelate blend plus oxide | Glutamine, taurine, levocarnitine, B vitamins including B6 41.1 mg, and other vitamins and minerals | Practitioner-only, after a consultation |
Details from manufacturer label information listed by Mr Vitamins, checked 8 October 2026. Check the AUST L number and full ingredients on the pack.
Three of these four products also contain vitamin B6. If you take more than one B6 product, add up the total, and stop and see your doctor if you notice tingling, burning or numbness.
What do AUST L and AUST R mean on a label?
Many magnesium supplements in Australia are listed medicines and show an AUST L number on the pack. For these, the Therapeutic Goods Administration (TGA) requires pre-approved low-risk ingredients and quality manufacturing, but does not check that they work before they are sold.
Instead, the company must hold evidence for its claims and give it to the TGA if asked. AUST L(A) products have had their claims assessed by the TGA before sale, and AUST R products are assessed for quality, safety and effectiveness.
Who should check with a healthcare professional first?
Speak to your doctor, pharmacist or a qualified practitioner before taking magnesium if any of these apply to you.
- Bone medicines called bisphosphonates: magnesium can reduce how well they are absorbed, so take them at least 2 hours apart.
- Some antibiotics: take tetracycline or quinolone antibiotics at least 2 hours before, or 4 to 6 hours after, magnesium.
- Diuretics (fluid tablets): some increase magnesium loss in urine, while others reduce it.
- Long-term reflux medicines called proton pump inhibitors: these can lower magnesium levels over time.
- Kidney problems: the risk of too much magnesium goes up when the kidneys cannot clear it well.
- Pregnancy or breastfeeding: your magnesium needs change, so get advice on the right amount.
Where does magnesium fit in a weight loss plan?
Magnesium works best as one part of a bigger plan. If your diet is low in magnesium, adding magnesium-rich foods is the simplest first step.
If you want wider support, you can browse our weight management range. Our practitioners can help you work out which options suit your goals and health.
Frequently asked questions
What is the best time of day to take magnesium?
There is no strong evidence that one time of day works better for weight. Taking it the same way each day matters more than the exact time.
If you take bisphosphonates or certain antibiotics, keep magnesium well apart from them. Your pharmacist can tell you how far apart.
Does magnesium glycinate help you lose weight?
There is no good evidence that magnesium glycinate causes weight loss. Reviews of magnesium trials found little or no change in body weight overall, and we found no trials testing glycinate for weight loss on its own.
Does magnesium make you poop?
It can, especially at high doses. Magnesium oxide, chloride, carbonate and gluconate are the forms most often linked to diarrhoea.
If this happens, the dose is likely too high for you. Any weight lost this way is fluid, not fat.
Can I take magnesium and vitamin D together?
Yes, many people take them together. The enzymes (body proteins) that turn vitamin D into its active forms appear to need magnesium to work.
How long should I take magnesium before I notice a difference?
In the weight loss trials, people took magnesium for 6 to 24 weeks, and most saw little change in weight. If you are taking it to fill a gap in your diet, ask a practitioner when to review how you are going.
Is it safe to take magnesium every day?
For most healthy adults, yes, if supplements provide no more than 350 mg a day unless a health professional advises otherwise. People with kidney problems should check with their doctor first, because their body clears magnesium less easily.
References
- Askari M, Mozaffari H, Jafari A, Ghanbari M, Darooghegi Mofrad M. The effects of magnesium supplementation on obesity measures in adults: a systematic review and dose-response meta-analysis of randomized controlled trials. Critical Reviews in Food Science and Nutrition. 2021;61(17):2921-2937. https://doi.org/10.1080/10408398.2020.1790498
- Rafiee M, Ghavami A, Rashidian A, Hadi A, Askari G. The effect of magnesium supplementation on anthropometric indices: a systematic review and dose-response meta-analysis of clinical trials. British Journal of Nutrition. 2021;125(6):644-656. https://doi.org/10.1017/S0007114520003037
- Veronese N, Dominguez LJ, Pizzol D, Demurtas J, Smith L, Barbagallo M. Oral magnesium supplementation for treating glucose metabolism parameters in people with or at risk of diabetes: a systematic review and meta-analysis of double-blind randomized controlled trials. Nutrients. 2021;13(11):4074. https://doi.org/10.3390/nu13114074
- Mah J, Pitre T. Oral magnesium supplementation for insomnia in older adults: a systematic review and meta-analysis. BMC Complementary Medicine and Therapies. 2021;21:125 (correction published 2024; results unchanged). https://doi.org/10.1186/s12906-021-03297-z
- Boyle NB, Lawton C, Dye L. The effects of magnesium supplementation on subjective anxiety and stress: a systematic review. Nutrients. 2017;9(5):429. https://doi.org/10.3390/nu9050429
- Gröber U, Werner T, Vormann J, Kisters K. Myth or reality: transdermal magnesium? Nutrients. 2017;9(8):813. https://doi.org/10.3390/nu9080813
- Uwitonze AM, Razzaque MS. Role of magnesium in vitamin D activation and function. Journal of the American Osteopathic Association. 2018;118(3):181-189. https://doi.org/10.7556/jaoa.2018.037
- National Health and Medical Research Council. Nutrient Reference Values for Australia and New Zealand: Magnesium. Canberra: Commonwealth of Australia; 2006. https://www.eatforhealth.gov.au/sites/default/files/2022-04/n35-magnesium_0.pdf
- Australian Bureau of Statistics. National Nutrition and Physical Activity Survey: Usual Nutrient Intakes, 2023. Table 6.7, Usual intake of magnesium, by age and sex. Released 17 March 2026. https://www.abs.gov.au/statistics/health/food-and-nutrition/usual-nutrient-intakes/2023
- healthdirect Australia. Magnesium. Last reviewed April 2025. https://www.healthdirect.gov.au/magnesium
- National Institutes of Health, Office of Dietary Supplements. Magnesium: Fact Sheet for Health Professionals. Updated 6 January 2026. https://ods.od.nih.gov/factsheets/Magnesium-HealthProfessional/
- Therapeutic Goods Administration. How are vitamins regulated in Australia? https://www.tga.gov.au/news/blog/how-are-vitamins-regulated-australia
This article is general information only and is not a substitute for advice from your healthcare professional.
Always read the label and follow the directions for use. If symptoms persist, talk to your health professional.
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