Vitamin D is a nutrient essential to the proper functioning of the body. Not only does it help maintain normal bone structure, notably 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 would have an insufficient concentration, and nearly 15% would suffer from a true deficiency.
Muscle weakness, pain, fatigue, frequent colds, or dry skin are signs that may indicate a vitamin D deficiency.
And beyond the muscular and bone problems that a vitamin D deficiency can cause, scientific studies show that it could also lead to weight gain. What does the research say about this?
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Do overweight people lack vitamin D?
Dilution of vitamin D in adipose tissue
Some researchers have studied a phenomenon: it seems that obese or overweight people have a greater vitamin D deficiency than non-obese people. And this is true even among young people (0-18 years), as shown by this meta-analysis.
Is this vitamin D deficiency a cause or a consequence of obesity? On this point, there are no clear and definitive 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 people.
There would therefore be less vitamin in the blood, and a more significant deficiency. To restore normal levels through supplementation, doses would then need to be increased compared to the general population.
Vitamin D deficiency could lead to obesity
But I should note that this is not the only explanatory factor for a lower vitamin D level in obese people. There may also be a lower intake of vitamin D-rich foods and less frequent sun exposure.
Moreover, vitamin D deficiency could lead to obesity, according to some studies.
In this study, 1,200 Spaniards were followed for 12 years. Non-obese participants at enrollment who had a vitamin D deficiency were shown to be more likely to become obese over the years than those with normal levels.
How would a vitamin D deficiency promote weight gain?
Vitamin D and hunger hormones
Several hypotheses have been proposed over the years about the potential link between vitamin D deficiency and an increased risk of obesity.
Studies I was able to find show that the vitamin D level may be correlated with adipokine production, molecules that are involved in many biological processes.
A normal level would inhibit the expression of these molecules by binding to a specific receptor, and would limit the inflammatory response. 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 the feeling of hunger, which would lead to long-term weight gain.
Vitamin D and dysregulation of insulin production
The relationship 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.
On peut donc supposer qu’un taux insuffisant pourrait être un facteur accélérant la formation d’une résistance à l’insuline. Indirectement, ce phénomène favoriserait alors le stockage des graisses et une prise de poids.
Should you consume more vitamin D to lose weight?
Conflicting studies
The research I was able to find on the subject is sometimes contradictory. While this review does not appear to show significant benefits, others are more promising.
A double-blind study including 77 female participants divided into two groups (a placebo group and a vitamin D group) showed that vitamin D intake in obese women over 12 weeks results in a significant reduction in fat mass.
However, weight and waist circumference did not change drastically in one group more than the other.
This other scientific study indicates that vitamin D consumption by obese people may increase adiponectin and leptin levels, which would make vitamin D an interesting avenue in the weight loss process.
Beware of vitamin D overdoses
However, there is no study showing that additional intake in people who are not deficient could have beneficial effects.
I strongly advise you not to overdose on vitamin D as it can cause headaches, vomiting, or extreme fatigue.
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My advice for increasing your vitamin D intake
To increase your vitamin D intake to avoid deficiencies and the associated symptoms, I suggest:
- to spend more time outdoors in the sun. Still avoid the hottest hours and always wear sunscreen
- to regularly eat fatty fish, such as salmon, an excellent source of vitamin D
- to include eggs in your meals
- to drink, if needed, 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.
