There’s nothing quite as frustrating as unexpected weight gain. You step on the scale hoping to be down a few pounds, but instead, you’ve tipped the scale in the opposite direction.

While exercise, diet, sleep, and stress are all essential pieces of the weight loss puzzle, could a nutrient deficiency be causing you to gain weight instead of losing it?

Weight gain can be a sign that something else is going on in your body—hormone imbalances, malabsorption, metabolic dysfunction—but it may also be a sign that your vitamin D levels are low.

Vitamin D is involved in everything from bone health and immune function, to yes, weight management. So, right now, we’re breaking down the link between vitamin D deficiency and weight gain and how you can tip the scales back in the right direction.

What Is Vitamin D And What Does It Do?

Although classified as a fat-soluble hormone, vitamin D functions more like a hormone with endocrine, paracrine, and autocrine functions 1. Vitamin D receptors are present in virtually all cell types, suggesting that vitamin D has functions beyond bone metabolism.

But for most people, the one function they know about with vitamin D is in bone health. The main role of the active form of vitamin D is calcium and phosphorus homeostasis; vitamin D regulates calcium uptake from the gut 2, 3.

Without sufficient vitamin D, the body cannot absorb calcium from the gut, which can lead to secondary hyperparathyroidism and bone loss, increasing the risk of osteoporosis, fractures, and mineralization defects, which long-term can lead to osteomalacia, muscle weakness, and a severe increase in the risk of fractures and falls.

That’s not it.

Vitamin D is also involved in other functions, some of which include:

  • Immune function
  • Mood
  • Inflammation
  • Weight management
  • Heart health
  • Growth and development

Signs Of A Vitamin D Deficiency

Despite being one of the most common nutrient deficiencies worldwide, most people are largely unaware that they’re low in vitamin D.

Many of the symptoms of low vitamin D can be chalked up to other causes, but not getting enough sunshine—or foregoing the oily fish—can result in some not-so-pleasant side effects that you’ll probably want to stay clear of.

Think you may be lacking vitamin D? Watch out for these signs and symptoms:

  • Frequent illness or infection
  • Fatigue and tiredness
  • Bone pain
  • Back pain
  • Impaired wound healing
  • Bone loss
  • Hair loss
  • Muscle pain
  • Weight gain
  • Anxiety and/or depression

Risk Factors For Vitamin D Deficiency

If you tick any of the boxes below, you may be at a greater risk for low levels of vitamin D 4, 5. But before you start stressing, know that there are plenty of ways to avoid deficiency status.

  • Skin pigmentation (darker skin has higher melanin levels, which makes vitamin D more difficult to absorb)
  • Overweight or obese
  • Plant-based diet
  • Limited exposure to sunlight
  • Frequent wearing of sunblock
  • Geography (northern climates receive less sun)
  • Heavy environmental pollution
  • Malabsorption syndromes (celiac disease, IBD, cystic fibrosis, etc.)
  • Elderly (>70 years)
  • Pregnancy

While vitamin D deficiency may result in unwelcome weight gain, it’s also linked to some major risk factors of several leading causes of death in the US, so getting serum levels up is non-negotiable for maintaining overall health.

5 Health Benefits Of Eating More Vitamin D

  1. Stronger bones: Because of its role in calcium and phosphate metabolism, vitamin D is essential for regulating bone metabolism 3. Vitamin D acts on the intestinal epithelium to stimulate calcium reabsorption from the intestines. It also interacts with parathyroid hormone (PTH) to stimulate the reabsorption of calcium and phosphate in the kidneys into the blood. In doing so, it supports the mineralization of the collagen matrix in bone to maintain health and strength 6.
  2. Healthier immune system: Most people aren’t aware of vitamin D’s involvement in immune function, but it plays critical roles in both the adaptive and innate branches of immune response, and low serum vitamin D has been linked to an increased risk of autoimmune conditions like rheumatoid arthritis, MS, diabetes, and IBD, along with increased susceptibility to infection 7, 8.
  3. Better mood: Sunshine, specifically vitamin D, is one of the most effective nutrients for treating seasonal affective disorder and other mood imbalances, which is likely due to the presence of vitamin D receptors in areas of the brain that regulate mood. Vitamin D also regulates the synthesis of serotonin, the “happy hormone” 9, 10.
  4. Less inflammation: As part of its role in the immune system, vitamin D controls inflammation levels via regulating the production of inflammatory cytokines and inhibiting the proliferation of pro-inflammatory cells 11. Excessive inflammation also makes it virtually impossible to lose weight and keep it off.
  5. Better glucose regulation: Balanced glucose and insulin responses are key to preventing weight gain, and vitamin D plays a role in glucose homeostasis by stimulating insulin release from pancreatic B-cells 12. Supplementation with vitamin D has also been shown to enhance insulin sensitivity, which helps to prevent weight gain.

Can Low Vitamin D Status Cause Weight Gain?

With all of that said, how do low vitamin D levels contribute to weight gain? Based on available research, you can take a sigh of relief because low vitamin D levels aren’t going to directly cause you to gain weight.

However, studies suggest a link between obesity and low serum vitamin D; individuals with a higher percentage of body fat appear to have lower vitamin D levels 13.

On top of that, vitamin D receptors are also widely distributed on human adipocytes, and serum concentrations of vitamin D may influence lipogenesis, lipolysis, adipogenesis, and adipocyte gene transcription 13.

Studies suggest that vitamin D levels may represent a predisposing factor to fat accumulation because vitamin D directly regulates differentiation and gene transcription in adipocytes via the VDR and nuclear VDR, but may also induce adipocyte cell death, thereby potentially helping to reduce fat mass 14.

Need proof? Several trials have shown a strong link between higher circulating vitamin D levels and greater fat and weight loss, along with improved fat oxidation and total energy expenditure 15, 16.

Final Thoughts

Keeping your vitamin D levels within the normal range is key if you want to lose weight and keep it off.

Whether you’re getting it from foods like salmon, sardines, and mackerel, or taking a clean vitamin D3 supplement when adequate sunshine isn’t available, maintaining proper vitamin D levels may be the key to supporting your weight loss efforts.


  1. WZ Mostafa, RA Hegazy. Vitamin D and the skin: Focus on a complex relationship: A review.J Adv Res. 2015;6(6):793-804.
  2. P Lips, NM van Schoor. The effect of vitamin D on bone and osteoporosis.Best Pract Res Clin Endocrinol Metab. 2011;25(4):585-591.
  3. I Krela-Kaźmierczak, A Szymczak, L Łykowska-Szuber, et al. The importance of vitamin D in the pathology of bone metabolism in inflammatory bowel diseases.Arch Med Sci. 2015;11(5):1028-1032.
  4. O Sizar, S Khare, A Goyal, et al. Vitamin D Deficiency. [Updated 2021 Jul 21]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from:
  5. MF Holick, TC Chen. Vitamin D deficiency: a worldwide problem with health consequencesAm J Clin Nutr. 2008;87(4):1080S-6S.
  6. C Aranow. Vitamin D and the immune system.J Investig Med. 2011; 59(6):881-886.
  7. M Hewison. Vitamin D and Innate and Adaptive Immunity. Vitamins & Hormones. 2011; 86:23-62.
  8. KL Munger, LI Levin, BW Hollis, NS Howard, A Ascherio. Serum 25-hydroxyvitamin D levels and risk of multiple sclerosis. 2006;296(23):2832-2838.
  9. DW Eyles, S Smith, R Kinobe, M Hewison, JJ McGrath. Distribution of the vitamin D receptor and 1 alpha-hydroxylase in human brain.J Chem Neuroanat. 2005;29(1):21-30.
  10. RP Patrick, BN Ames. Vitamin D and the omega-3 fatty acids control serotonin synthesis and action, part 2: relevance for ADHD, bipolar disorder, schizophrenia, and impulsive behavior. FASEB J. 2015;29(6):2207-2222.
  11. K Yin, DK Agrawal. Vitamin D and inflammatory diseases.J Inflamm Res. 2014;7:69-87.
  12. E Yousefi Rad, M Djalali, F Koohdani, et al. The Effects of Vitamin D Supplementation on Glucose Control and Insulin Resistance in Patients with Diabetes Type 2: A Randomized Clinical Trial Study.Iran J Public Health. 2014;43(12):1651-1656.
  13. ES LeBlanc, JH Rizzo, KL Pedula, et al. Associations between 25-hydroxyvitamin D and weight gain in elderly women.J Womens Health (Larchmt). 2012;21(10):1066-1073.
  14. IN 1,25-Dihydroxyvitamin D3 induces Ca2+-mediated apoptosis in adipocytes via activation of calpain and caspase-12.Biochem Biophys Res Commun. 2009;384(1):18-21.
  15. D Teegarden, KM White, RM Lyle, et al. Calcium and dairy product modulation of lipid utilization and energy expenditure.Obesity (Silver Spring). 2008;16(7):1566-1572.
  16. DR Shahar, D Schwarzfuchs, D Fraser, et al. Dairy calcium intake, serum vitamin D, and successful weight lossAm J Clin Nutr. 2010;92(5):1017-1022.