Successful weight loss depends on the lifestyle changes we make. For instance, instead of a sedentary lifestyle, we should be more active and exercise regularly. Instead of an unhealthy diet, we should consume healthier foods. You see, our body requires a wide range of nutrients to function properly and that also includes weight management. In order to slim down, you need to focus on the intake of protein, healthy fats, and various vitamins. One of those vitamins is vitamin D. In this post we’re going to focus on the importance of vitamin D on weight loss.

Vitamin D Overview 

Vitamin D, or the sunshine vitamin, is a fat-soluble vitamin produced when UV rays from sunlight strike the skin and trigger the synthesis of this micronutrient. Also naturally present in some foods, added to others, and available in the form of dietary supplements, vitamin D is crucial for our health. 

You see, vitamin D promotes the absorption of calcium in the gut. At the same time, sunshine vitamin maintains adequate calcium and phosphate concentrations necessary for bone mineralization. The body needs vitamin D for bone growth and bone remodeling. 

Although vitamin D is primarily associated with bone health, its functions extend to attenuating inflammation and modulation of several processes in the body ranging from cell growth to immune function and glucose metabolism (1).

Low Vitamin D and Excess Weight 

The human body needs specific amounts of different macro- and micronutrients to function properly and maintain weight. When it doesn’t get sufficient levels of those nutrients, the body is bound to go through some changes. These changes manifest themselves in some symptoms, increased risk of several health conditions, and weight gain even. Low levels of vitamin D are just like that.

A study from the Journal of Clinical Endocrinology and Metabolism found that levels of vitamin D are lower in obese than non-obese subjects. Scientists concluded the concentrations of this micronutrient fall with increasing adiposity i.e. excess weight (2). The same journal published a different study that found that low levels of vitamin D are associated with higher body fat percentage (3).

Basically, evidence shows overweight or obese persons tend to have low vitamin D levels.

What’s the connection between low vitamin D and being overweight or obese?

A specific answer to this question doesn’t exist. Various theories explain the relationship between the two. One theory is that obese men and women tend to consume fewer vitamin D-rich foods as their diet primarily consists of unhealthy meals. 

Behavioral factors could also play a role. Overweight or obese men and women tend to expose less skin. As a result, the body doesn’t get much vitamin D from the sun. Remember, the sun’s UV rays trigger the synthesis of vitamin D when they enter your skin.

Enzymes are yet another connection between low vitamin D and obesity. The body needs certain enzymes to convert vitamin D into its active form. The levels of these enzymes may differ between obese and normal-weight persons (4).

Moreover, a study from the journal Obesity found once vitamin D concentration in obese persons is adjusted for body size, there is no difference between levels of this micronutrient between obese and non-obese individuals (5). This means the vitamin D needs depend on your size. In other words, obese individuals need more vitamin D to reach the same blood concentration thus explaining why they are more likely to be deficient. 

Weight Loss Affects Vitamin D

Just like levels of this vitamin play a role in your weight, slimming down can affect vitamin D too. Decreased body size also means the requirement for vitamin D is reduced as well. That being said, the amount of vitamin D in the body may remain the same when you slim down. As a result, the levels would increase (6, 7). 

The degree of weight loss affects the extent to which vitamin D levels rise. Even modest weight loss may lead to elevated vitamin D. In a study from the American Journal of Clinical Nutrition, subjects who lost 15% of body weight experienced Vitamin D increase three times greater than those who lost 5% to 10% of body weight (8).

Increase Vitamin D to Slim Down

Since excess weight is associated with lower vitamin D levels, it’s impossible not to wonder if you could slim down by increasing the concentration of the sunshine vitamin. Science says YES!

Getting enough vitamin D could help decrease body fat and enhance weight loss. One study followed 218 overweight and obese women for 12 months. All women had to adhere to a specific exercise routine and a calorie-restricted diet. However, half of them received vitamin D whereas their counterparts were in a placebo group. Results showed women from the vitamin D group achieved better weight loss. They lost about 7 lbs (3.2kg) more than women from the placebo group who didn’t have adequate levels of vitamin D in the blood (9).

What we can learn from this study is that increased intake of vitamin D can support weight loss. While a study from the Nutrition Journal found subjects who took vitamin D supplements for 12 weeks didn’t experience weight loss, their body fat decreased (10).

As you can see, to slim down and reduce body fat, you need enough vitamin D. But this micronutrient can do a lot more than that. You see, sufficient vitamin D levels can prevent weight gain. The Journal of Women’s Health published a study of 4600 elderly women where higher levels of vitamin D were associated with less weight gain (11).

Even though more research is necessary on this subject, getting enough vitamin D could support your weight loss efforts or aid weight management. This is particularly important if you tend to regain weight easily. 

Vitamin D Decreases the Formation of New Fat Cells

Despite studies showing vitamin D supports weight loss, the underlying mechanisms are still unclear. A potential mechanism of action is the impact of vitamin D on fat cells and body fat in general. 

Evidence shows vitamin D could reduce the development of new fat cells in the body (12). As a result, there is less body fat to accumulate. This can not only prevent weight gain but also make it easier to slim down.

Moreover, the Nutrition journal published a study that showed vitamin D could work by suppressing the storage of adipocytes (fat cells). In turn, sunshine vitamin effectively decreases the accumulation of fat in the body (13).

When we’re talking about vitamin D and body fat it’s useful to mention an interesting study from the British Journal of Nutrition. The study revealed supplementation with vitamin D and calcium increased fat mass loss in subjects. Extra calcium and vitamin D also exhibited an appetite suppressing effect (14).

Vitamin D Increases Serotonin

Serotonin is a neurotransmitter that acts on every part of our body. This neurotransmitter impacts emotions and motor skills. It is also considered a mood stabilizer. The activity of serotonin is necessary for basic human functions such as eating, sleeping, and digesting food.

What most of us don’t know is that vitamin D increases levels of serotonin (15). A growing body of evidence confirms serotonin can control your appetite and increase satiety, thus reducing body weight and lowering the intake of calories (16).

A major enemy of successful weight loss is the tendency to overeat. Most people consume a lot more calories than the body needs during the day. If the calorie intake is consistently higher than the number of calories you burn through activity, you end up gaining weight. As you try and try to slim down, overeating acts as a major obstacle. 

For persons who manage to lose weight, overeating can lead to regaining lost pounds. Therefore, appetite control is crucial. 

Whether you want to slim down or maintain weight in a healthy range, you need to avoid overeating and cravings for unhealthy foods. To do so, it’s useful to consume fiber-rich foods. But, you should also enrich your diet with vitamin D or take supplements. Through elevated serotonin, you could be able to control your appetite for healthy and sustainable weight loss.

The effect of vitamin D on serotonin goes beyond appetite suppression. Serotonin affects your mood as well. So, low vitamin D and reduced serotonin could impair your mood and produce fatigue. As a result, you’re not motivated to exercise and don’t even feel like you have the energy for it. That’s where vitamin D steps in. By elevating serotonin, the sunshine vitamin could help this neurotransmitter improve your mood and energy levels. What happens next is that you’re in a good mood, feel energetic, and are motivated to work out. All this translates to a successful weight loss. 

Vitamin D Benefits Testosterone Levels

Vitamin D has more roles and functions than we realize. One of those roles is its positive impact on testosterone levels. Sunshine vitamin is linked with higher testosterone (17), which could be yet another mechanism behind weight loss. 

A study from Hormone and Metabolic Research had some interesting findings on this subject. Scientists enrolled 165 men who took either vitamin D or placebo for 12 months. Men who received vitamin D had a higher increase in testosterone levels than their counterparts from the placebo group (18). 

What makes the above mentioned findings important is that higher testosterone levels can decrease body fat and help you achieve a long-term, sustainable weight loss without recidivism (19, 20).

How does testosterone lead to weight loss and reduction in body fat? This hormone uses a multifaceted approach to deliver its effects. Testosterone can accelerate metabolic rate (21). A faster metabolism means you get to burn more calories. Also, just like vitamin D, testosterone could block the formation of new fat cells (22). 

Vitamin D Has Antioxidant and Anti-inflammatory Properties

Vitamin D may have antioxidant properties (23) meaning it could act to neutralize free radicals and damage they would cause. Excess weight is strongly associated with increased oxidative stress. Through antioxidant roles, vitamin D could support weight loss and its maintenance. 

Moreover, at the beginning of this post, we’ve mentioned vitamin D could attenuate inflammation. The same as with oxidative stress, excess weight is linked to an inflammatory state. By lowering inflammation vitamin D could help you slim down.

Vitamin D Improves Muscle Strength 

The goal of weight loss efforts is not just to lose body fat only. It’s also important to tone the body for a more defined look. That’s why you need to include strength training into your daily routine. This type of training increases muscle strength. Vitamin D supplementation could also benefit your muscles and their strength.

People with a higher lean muscle mass also tend to have higher levels of active vitamin D. That means an active form of vitamin D may help optimize muscle strength (24). Interestingly, this impact on muscle strength was observed in women, but not in men. Of course, a lot more studies on this topic are necessary to get all the facts.

Obtaining enough vitamin D through diet or supplements could help with energy output during vigorous workouts. At the same time, the body stores vitamin D thus allowing it to support muscle repair. You see, muscle tissue has special receptors for vitamin D that allow this micronutrient to strengthen muscle fibers and promote recovery from muscle damage.

Regular workouts are an integral component of a healthy lifestyle and effective weight loss strategy. But, workouts can be difficult on muscles. For that reason, supplementation with vitamin D could be useful. The sunshine vitamin can strengthen muscles and also support their recovery. This can minimize the risk of injuries and allow you to improve athletic performance. You’ll do more in the gym and experience better results. 

Vitamin D Reduces Insulin Resistance

Insulin resistance increases blood sugar levels and paves the way to type 2 diabetes. If you already have diabetes or insulin resistance itself, it can be tricky to slim down or maintain weight in a healthy range. Tricky, but not impossible! 

Studies show vitamin D supplementation can reduce insulin resistance and decrease excessive insulin release in response to elevated blood sugar in persons with insulin resistance. In other words, vitamin D increases insulin sensitivity. For that reason, deficiency in vitamin D is a risk factor for metabolic syndrome and type 2 diabetes (25).

By promoting insulin sensitivity, vitamin D could allow you to slim down. It’s useful to keep in mind that persons with insulin resistance tend to overeat. We’ve discussed the dangers of overeating above.

How Much Vitamin D Do You Need?

Getting the right amount of vitamin D a day helps you avoid deficiencies and obtain everything this micronutrient has to offer. 

Adults who are 19 to 50 years old need 600IU (15mcg) of vitamin D during the day. The same amount is also necessary for older adults (51-70 years) and teenagers (14-18 years). Men and women older than 70 years need 800IU (20mcg) a day.

Ideally, you should obtain vitamin D through diet. But, if your diet doesn’t deliver enough vitamin D during the day, supplementation could be useful. If you’re taking supplements, you need to stick to the dosage instructions provided by the manufacturer. Avoid increasing or decreasing dosage on your own.

Sources of Vitamin D

The truth is that few foods contain vitamin D naturally, but some of the best sources are:

  • Fatty fish (salmon, trout, sardines, tuna)
  • Beef liver
  • Cheese
  • Egg yolks
  • Mushrooms
  • Cod liver oil
  • Fortified cereal
  • Fortified milk


Vitamin D has important functions in the body. We usually associate it with the immune system and bone health. A growing body of evidence confirms vitamin D could support weight loss and prevent weight gain. The sunshine vitamin works through several mechanisms to deliver its effects. The need for vitamin D depends on the weight of a person, which explains why overweight or obese persons tend to be deficient. To slim down successfully, you may want to enrich your diet with vitamin D or take supplements. But, vitamin D is not a replacement for a healthy diet and regular physical activity. 



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