Hi! I'm Stelios Pantazis. Ι'm a doctor and I specialize in medical nutrition and metabolic disorders. Today, I'm presenting a subject added to our regular schedule concerning some studies that show that vitamin D affects weight. January is the month when many people traditionally start diet and weight loss plans. As an expert in medical nutrition, during this period, I see many people that seek help for this purpose in the two medical nutrition centers that I lead. In recent years, among the many reasons for weight increase that I've noticed and often deal with, vitamin D deficiency has been added as one more reason. Today, we'll see how vitamin D affects weight increase and in which cases the administration of vitamin D can help you lose weight. Vitamin D is produced by the body when the skin is exposed to the sun. As the same happens in plants and animals, when they're exposed to the sun, we can take the vitamin D that they produce before we consume them. However, rarely does someone achieve normal levels of vitamin D in their blood only with exposure to the sun and diet. Due to reasons that I've explained in a previous video, it has been estimated that 50% of the people don't have enough vitamin D in their blood. But vitamin D is very important not only in metabolism, but also for strong bones, good function of the brain and the immune system. In a previous video, I've explained how the sufficiency of vitamin D may even protect from COVID-19. Recent studies, however, claim that the sufficiency of vitamin D in our diet may even protect from weight increase. This observation started when it was observed that overweight people often have low levels of vitamin D. Therefore, the question arose if low levels of vitamin D may lead to weight increase. We know that people with increased fat have an increased need for vitamin D, because vitamin D is a lipophilic hormone and, after it is consumed, a large part of it is stored in the fat, therefore it's not available for use. It is estimated that an overweight person needs 50% more vitamin D than people with normal weight. However, the co-occurrence of low levels of vitamin D and increased weight can't convince us that the low intake of vitamin D may lead to increased weight, because there may be other reasons that better explain this association. In order to prove that vitamin D protects from weight increase or that vitamin D helps in weight loss, studies should be carried out that do exactly this: vitamin D is administered to overweight people and it is observed if they'll lose weight. Of course, there has to be a comparison group, namely a group of people that will take something similar to vitamin D, a placebo, that is. Fortunately, such studies have been carried out. For example, in such a study, the female participants were divided into two groups. The first group took vitamin D and the second one took a placebo. The study lasted 12 week and, after its completion, it was observed that the women that took vitamin D had lost 2.7 kg of fat, while the women that took the placebo had lost 0.5 kg of fat. At the same time, the women that took vitamin D had also gained 1.4 kg more muscle tissue than the other group. Can we conclude from this study that vitamin D is the weight-loss pill that we all dream of? Not yet. More and larger studies must be carried out. But some similar studies have been carried out again. A study that gathered all of them has shown that the administration of vitamin D can help in fat loss. However, the fat loss described in the studies, albeit reliable and useful, is not big. Furthermore, the loss may be small or inexistent in women with normal levels of vitamin D. Therefore, what should you do? The most significant way to lose weight is the healthy diet. At the same time, however, you should do blood tests for vitamin D, at least once a year, in February or March, when the levels of vitamin D in the blood are the lowest during the year. If the levels of vitamin D in your blood are low, change your exposure to the sun and your diet and, if needed, take supplements, in order to make sure that your vitamin-D levels in your blood are normal, so that they don't affect your metabolism. Thank you very much!

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