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Information on the latest vitamin D news and research.

Find out more information on deficiency, supplementation, sun exposure, and how vitamin D relates to your health.

Obesity and vitamin D deficiency, which causes which?

Observational studies have consistently reported an increased risk of vitamin D deficiency in those who are obese. However, the underlying explanations and direction of causality are unclear. Does obesity cause vitamin D deficiency, does vitamin D deficiency cause obesity or is it a little of both?

Activated vitamin D (1,25-dihydroxyvitamin D) may influence the mobilization of free fatty acids from the adipose tissue as well as metabolism of fat cells. Rat experiments have shown that large doses of vitamin D lead to increases in energy expenditure, a mechanism of weight loss. However, three randomized controlled trials testing the effect of vitamin D supplementation on weight loss in obese or overweight individuals showed no effect. On the other hand, there have been randomized controlled trials that have shown a very modest weight reduction after vitamin D supplementation, too.

So which is it? A recent new kind of genetic study, called Mendelian randomization, wanted to find out, does obesity more cause vitamin D deficiency, or does vitamin D deficiency more cause obesity?

In Mendelian randomization, cause is assumed when associations exist between genetic variants that mimic the influence of a deficiency and the outcome of interest. Because gene variants do not change over time and are inherited randomly, they are not prone to confounding and are free from the possibility of reverse causation. Thus, if a lower vitamin D status leads to obesity, genetic variants associated with lower 25(OH)D concentrations should be associated with obesity, and if obesity leads to a lower vitamin D status, then genetic variants associated with obesity should be associated with lower 25(OH)D concentrations.

Recently, Doctor Karani Vimaleswaran, working under senior author Professor Elina Hyppönen, both of the UCL Institute of Child Health in London, used Mendelian randomization to find that obesity more causes low vitamin D rather than the other way around.

Vimaleswaran KS, et al. Causal relationship between obesity and vitamin D status: bi-directional Mendelian randomization analysis of multiple cohorts. PLoS Med. 2013;10(2):e1001383.

The researchers created a score based on BMI-related gene variants and 25(OH)D scores based on vitamin D gene variants. Using information on more than 42,000 participants from 21 studies, the researchers showed that the gene variants for obesity was associated with both BMI and with 25(OH)D levels among the study participants. Based on this information, they calculated that each 10% increase in BMI will lead to about a 4% decrease in 25(OH)D concentrations. By contrast, although 25(OH)D scores were strongly associated with 25(OH)D levels, neither score was associated with BMI.

The authors concluded:

“These findings suggest that a higher BMI leads to a lower vitamin D status whereas any effects of low vitamin D status on BMI are likely to be small. That is, these findings provide evidence for obesity as a causal factor in the development of vitamin D deficiency but not for vitamin D deficiency as a causal factor in the development of obesity. These findings suggest that population-level interventions to reduce obesity should lead to a reduction in the prevalence of vitamin D deficiency and highlight the importance of monitoring and treating vitamin D deficiency as a means of alleviating the adverse influences of obesity on health.”

This makes sense to me. While vitamin D might help you feel and be more active, while vitamin D may play a role in adipose tissue, clearly these effects are minute compared to the heavy hand obesity plays in diluting your vitamin D stores and making you deficient. It’s important to recognize that if you weigh more, you will need more vitamin D than someone who weighs less.

  About: John Cannell, MD

Dr. John Cannell is founder of the Vitamin D Council. He has written many peer-reviewed papers on vitamin D and speaks frequently across the United States on the subject. Dr. Cannell holds an M.D. and has served the medical field as a general practitioner, emergency physician, and psychiatrist.

6 Responses to Obesity and vitamin D deficiency, which causes which?

  1. Rita and Misty says:

    I did lose 30% of my body weight when I raised my 25(OH)D level from 32 ng/ml to 74 ng/ml…I did not change my diet, nor did I change my exercise patterns.

    I wonder (often) if my higher 25(OH)D level corrected a fairly sub-clinical thyroid problem…

    (awesome graphics, btw) :)

  2. Magic says:

    I agree with the findings. I don’t think that D3 by itself is a weight loss miracle. Perhaps the obese are so embarrassed to be seen that it could be a contributing factor. (Never in the sun.)

    What happened to you has to be classified as a miracle, Rita. So many good things have happened to me that I have never included weight loss among them.

    At my age of almost 80 friends are dying at an alarming rate. None, however, that have been ingesting D3. Some doctors out here are still shocked when anything over 1000 D3 are mentioned.

    Magic

  3. Rita and Misty says:

    Hi Magic,

    I think vitamin D can have a positive impact on the thyroid gland. And, my thyroid numbers were always in that (very slightly) hypo range. Supplementing with high doses of D improved the health of my thyroid.

    Plain and simple!!!

    Certainly, I do believe in miracles.

    For example, it was a miracle I found this awesome site and organization. I literally just fell onto the Vitamin D Council Facebook page (and my life has never been the same :) Really–Truly lol)

    But, I think my hormonal health improved because high doses of vitamin d made my thyroid gland healthy.

    Female hormonal healthy is directly related to a healthy thyroid–in my most humble opinion.

    :)

  4. IAW says:

    I agree with Dr. Cannell’s statement “It’s important to recognize that if you weigh more, you will need more vitamin D than someone who weighs less.” I am not convinced yet that “low vitamin d levels” cannot cause obesity to happen. Whether this is a director result or like Rita said an indirect improvement in thyroid function. We also know that a lot of studies use too small of an amount of Vitamin D to cause any noticeable or barely noticeable changes.

  5. Rita and Misty says:

    By the way: it takes quite a bit of gumption on my part to share my idiopathic early menopause health story with people; but I only hope that a few endocrinologists are reading me and perhaps will consider high dose supplementation for those patients diagnosed with such a condition.

    After my personal experience, I tend to believe there is no such thing as idiopathic early menopause….

    If I can keep just one woman from suffering how I suffered for six years I will be content.

  6. I am 50 to 60lbs overweight. My work situation has made it difficult for me to loose those pounds. However, that has just changed. My D level is close to 60 ng/ml. I am 65 and no longer have chronic knee pain (no medical intervention). It will be much easier for me to be active again because I feel better. In turn that should help me loose weight.