Vitamin D is an essential nutrient for the proper functioning of the body. Not only does it help maintain normal bones, mainly through its action on calcium and phosphorus, but it also plays a major role in the immune system.
And yet, vitamin D deficiencies are common. According to INSERM, more than 50% of the French population has insufficient levels, and nearly 15% suffer from a true deficiency.
Muscular weakness, pain, fatigue, frequent colds, or even dry skin are signs that may indicate a vitamin D deficiency.
Beyond the muscular and bone disorders that a vitamin D deficiency can cause, scientific studies show it could also lead to weight gain. What does the research say about this?
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Are overweight people lacking in vitamin D?
Dilution of vitamin D in adipose tissue
Some researchers have focused on a phenomenon: it seems that obese or overweight people may have a more significant vitamin D deficiency than non-obese individuals. This is true even among young people (0-18 years old), as shown in this meta-analysis.
Is this vitamin D deficiency a cause or a consequence of obesity? On this point, there are no clear and defined conclusions from scientific studies.
According to this review, this phenomenon could be explained by the dilution of vitamin D in the adipose tissue of obese individuals.
As a result, there would be less vitamin D in the blood, and a more significant deficiency. To restore normal levels through supplementation, doses would have to be increased compared to the normal population.
Vitamin D deficiency could lead to obesity
However, I should note that this is not the only explanatory factor for lower vitamin D levels in obese people. A potentially lower consumption of vitamin D-rich foods and less sun exposure can also be observed.
Aside from this, vitamin D deficiency could lead to obesity, according to some studies.
In this study, 1200 Spaniards were followed for 12 years. Those who were non-obese at inclusion and had a vitamin D deficiency were more likely to become obese over the years than those with normal levels.
How could a vitamin D deficiency promote weight gain?
Vitamin D and hunger hormones
Several hypotheses have been proposed over the years on the potential link between vitamin D deficiency and increased risk of obesity.
Studies I found show that the vitamin D level might be correlated with the production of adipokines, molecules involved in numerous biological processes.
A normal level would inhibit the expression of these molecules by binding to a specific receptor, limiting the inflammatory phenomenon. It would also affect the normal production of the satiety hormone, leptin.
A deficiency could thus disrupt this regulation of adipokines, reduce leptin production, and increase hunger, leading to weight gain in the long term.
Vitamin D and the disruption of insulin production
The link between insulin and vitamin D was the subject of a review in 2019. It showed that a normal level of this vitamin can prevent epigenetic alterations associated with insulin resistance and diabetes.
It can thus be assumed that an insufficient level could be a factor accelerating the development of insulin resistance. Indirectly, this phenomenon would then promote fat storage and weight gain.
Should you consume more vitamin D to lose weight?
Conflicting studies
The research I found on the subject is sometimes conflicting. While this review seems to not show significant benefits, others are more promising.
A double-blind study involving 77 participants divided into two groups (a placebo group and a vitamin D group) showed that vitamin D consumption in obese women over 12 weeks led to a significant reduction in fat mass.
However, weight and waist circumference did not drastically change in one group compared to the other.
This other scientific study suggests that vitamin D intake by obese individuals could increase levels of adiponectin and leptin, making vitamin D an interesting option in the weight loss process.
Beware of vitamin D overdoses
However, there is no study showing that additional intake in non-deficient individuals could have beneficial effects.
I strongly advise against overdosing on vitamin D as it may cause headaches, vomiting, or severe fatigue.
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My tips to increase your vitamin D intake
To increase your vitamin D intake to prevent deficiencies and associated symptoms, I suggest:
- spending more time outdoors in the sun. Still, avoid the hottest hours and always wear sun protection
- regularly consuming fatty fish, such as salmon, an excellent source of vitamin D
- adding eggs to your meals
- drinking, if necessary, vitamin D-fortified milk
Sources and scientific studies
Fiamenghi VI, Mello ED, 2021, Vitamin D deficiency in children and adolescents with obesity: a meta-analysis
Migliaccio S, Di Nisio A, Mele C, Scappaticcio L, Savastano S, Colao A, 2019, Obesity and hypovitaminosis D: causality or casualty?
González-Molero I, Rojo-Martínez G, Morcillo S, 2013, Hypovitaminosis D and incidence of obesity: a prospective study.
Nimitphong H, Guo W, Holick MF, Fried SK, Lee MJ, 2021, Vitamin D Inhibits Adipokine Production and Inflammatory Signaling Through the Vitamin D Receptor in Human Adipocytes.
Szymczak-Pajor I, Śliwińska A, 2019, Analysis of Association between Vitamin D Deficiency and Insulin Resistance.
Mason C, Xiao L, Imayama I, Duggan C, 2014, Vitamin D3 supplementation during weight loss: a double-blind randomized controlled trial.
Salehpour A, Hosseinpanah F, Shidfar F, 2012, A 12-week double-blind randomized clinical trial of vitamin D₃ supplementation on body fat mass in healthy overweight and obese women.
Aya Mousa, Negar Naderpoor, Kirsty Wilson, 2019, Vitamin D supplementation increases adipokine concentrations in overweight or obese adults.
