5 Supplements for Weight Loss a Dietitian Recommends: Part 2

For Part 1, please click here.

As a Dietitian, I get asked about supplements more than anything else. As an RDN who’s worked with thousands of men and women on their metabolic health, I want to walk you through some of the research on a few supplements. You deserve to know where your money is actually well spent.

The first supplement I want to go over is Vitamin D3. Vitamin D deficiency is one of the most common deficiencies we see clinically, and it’s not by a small margin. If you’re insulin-resistant or carrying extra weight, this likelihood increases even more, as low vitamin D status tends to track right alongside higher body weight and adiposity. Among women going through a weight-loss program, those who increased their vitamin D levels to a healthy range lost more weight, lowered their waist circumference, and lost more fat than those who didn’t correct their deficiency ^{[4, 5, 8]}.

A large 2026 meta-analysis that specifically examined obesity-associated metabolic syndrome found that vitamin D3 significantly reduced visceral fat. That same meta-analysis showed improvements in fasting glucose, HOMA-IR, and LDL cholesterol. Vitamin D can be a powerful adjunct to diet, especially for those with suboptimal levels ^[8].

The second supplement I’d like to go over is magnesium glycinate, the quiet powerhouse. Like vitamin D3, the vast majority of people do not consume enough magnesium. Magnesium is involved in glucose metabolism, insulin sensitivity, muscle function, blood pressure regulation, and so much more. Glycinate is a fantastic form because it’s well absorbed and has fewer GI side effects than other forms of magnesium. A large dose-response analysis found that magnesium reduced BMI, with the effect driven mostly by people who started out magnesium-deficient, insulin-resistant, or already overweight or obese. A separate analysis specifically examined waist circumference and found a real reduction; magnesium reduced waist circumference by about 2 centimeters ^[1,9].

In those with prediabetes, magnesium raised HDL in just twelve weeks. In those with type 2 diabetes, it lowered both systolic and diastolic blood pressure, with the biggest effect at higher doses and after more than twelve weeks of use ^[2,10].

The last thing to understand about magnesium is that it’s a required cofactor for vitamin D metabolism, so if you’re supplementing vitamin D but you’re also low in magnesium, your body might not use or convert vitamin D as it should ^[5].

Next, let’s move to apple cider vinegar. I know by now you’ve seen the gummies and the “1 tablespoon before each meal” advice. The truth is, the acetic acid in ACV actually helps; it consistently lowers fasting blood sugar, A1C, and total cholesterol, with the strongest effect showing up in people with type 2 diabetes. Some analyses even show a 30-point drop in fasting glucose. It can also help bring down triglycerides in people who are overweight or diabetic ^[6,11].

Omega-3’s are another one of the supplements I don’t go without; these effects are especially strong if you combine them with other lifestyle modifications. A meta-analysis of 15 RCTs found significant reductions in body weight, BMI, waist circumference, and total body fat percentage. Another review found that those taking fish oils lose more than ~0.59 kg more than controls. When combined with lifestyle modifications, a 21-RCT meta-analysis in overweight/obese individuals found significant reductions in waist circumference and waist-to-hip ratio ^{[12, 13, 14]}.

Lastly, let’s go through the research on Fenugreek. It has been used for centuries to treat blood sugar and digestive complaints, but modern research shows it can also reliably improve your lipid panel. Lower total cholesterol, lower triglycerides, lower LDL, and even a bump in HDL. A broader meta-analysis of metabolic syndrome found that fenugreek also lowered fasting glucose, systolic blood pressure, and waist circumference ^{[3, 7, 15]}.

These supplements work with your body’s chemistry, and taking them alongside a healthy diet and lifestyle will give you the best chance of reaching your health goals.

References

1. 1. 1. Askari, M., Mozaffari, H., Jafari, A., Ghanbari, M., & Darooghegi Mofrad, M. (2020). 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.
      2. Asbaghi, O., Hosseini, R., Boozari, B., et al. (2021). The effects of magnesium supplementation on blood pressure and obesity measure among type 2 diabetes patients: A systematic review and meta-analysis of randomized controlled trials. Biological Trace Element Research.
      3. Askarpour, M., Alami, F., Campbell, M. S., et al. (2020). Effect of fenugreek supplementation on blood lipids and body weight: A systematic review and meta-analysis of randomized controlled trials. Journal of Ethnopharmacology.
      4. Mason C, Xiao L, Imayama I, et al. Vitamin D3 supplementation during weight loss: a double-blind randomized controlled trial. Am J Clin Nutr. 2014;99(5):1015-1025. doi:10.3945/ajcn.113.073734
      5. Demay, M. B., Pittas, A. G., Bikle, D. D., Diab, D. L., Kiely, M. E., Lazaretti-Castro, M., Lips, P., Mitchell, D. M., Murad, M. H., Powers, S., Rao, S. D., Scragg, R., Tayek, J. A., Valent, A. M., Walsh, J. M. E., & McCartney, C. R. (2024). Vitamin D for the prevention of disease: An Endocrine Society clinical practice guideline. The Journal of Clinical Endocrinology & Metabolism, 109(8), 1907–1947. https://doi.org/10.1210/clinem/dgae290 (OUP Academic)
      6. Hadi, A., Pourmasoumi, M., Najafgholizadeh, A., Clark, C. C. T., & Esmaillzadeh, A. (2021). The effect of apple cider vinegar on lipid profiles and glycemic parameters: A systematic review and meta-analysis of randomized clinical trials. BMC Complementary Medicine and Therapies.
      7. Heshmat-Ghahdarijani, K., Mashayekhiasl, N., Amerizadeh, A., Teimouri Jervekani, Z., & Sadeghi, M. (2020). Effect of fenugreek consumption on serum lipid profile: A systematic review and meta-analysis. Phytotherapy Research.
      8. Huang, Q., Zhan, J., Gui, Y., Ma, M., & Li, E. (2026). Effects of different vitamin D supplements on body fat distribution and glucolipid metabolism in patients with obesity-associated metabolic syndrome: A meta-analysis. Medicine, 105(8), e47436. https://doi.org/10.1097/MD.0000000000047436 (PubMed Central (PMC))
      9. Rafiee, M., Ghavami, A., Rashidian, A., Hadi, A., & Askari, G. (2021). The effect of magnesium supplementation on anthropometric indices: A systematic review and dose-response meta-analysis of clinical trials. British Journal of Nutrition.
      10. Salehidoost, R., Taghipour Boroujeni, G., Feizi, A., Aminorroaya, A., & Amini, M. (2022). Effect of oral magnesium supplement on cardiometabolic markers in people with prediabetes: A double blind randomized controlled clinical trial. Scientific Reports. (Nature)
      11. Tehrani, S. D., Keshani, M., Rouhani, M. H., et al. (2023). The effects of apple cider vinegar on cardiometabolic risk factors: A systematic review and meta-analysis of clinical trials. Current Medicinal Chemistry.
      12. Li YH, Sun TY, Wu YY, et al. Higher erythrocyte n-3 polyunsaturated fatty acid were associated with a better profile of DXA-derived body fat and fat distribution in adults. Int J Obes (Lond). 2020;44(9):1884-1892. doi:10.1038/s41366-020-0569-8.
      13. Bender N, Portmann M, Heg Z, Hofmann K, Zwahlen M, Egger M. Fish or n3-PUFA intake and body composition: a systematic review and meta-analysis. Obes Rev. 2014;15(8):657-665. doi:10.1111/obr.12189.
      14. Du S, Jin J, Fang W, Su Q. Does fish oil have an anti-obesity effect in overweight/obese adults? A meta-analysis of randomized controlled trials. PLoS One. 2015;10(11):e0142652. doi:10.1371/journal.pone.0142652.
      15. Fakhr L, Chehregosha F, Zarezadeh M, Chaboksafar M, Tarighat-Esfanjani A. Effects of fenugreek supplementation on the components of metabolic syndrome: a systematic review and dose-response meta-analysis of randomized clinical trials. Pharmacol Res. 2023;187:106594. doi:10.1016/j.phrs.2022.106594.