If you think you're doing everything right to lose or maintain weight, but you just keep gaining instead, a vitamin deficiency may be to blame. According to research published in ISRN Endocrinology in 2012, obese individuals tend to have high rates of nutrient deficiencies. Although many foods in the U.S. are fortified with vitamins such as vitamin D or the B-vitamins, if your diet contains low-quality food, you may not be getting adequate amounts of certain vitamins to help your body burn energy and prevent weight gain.
Two classes of vitamins should be a part of your daily diet. Water-soluble vitamins such as vitamin C and B vitamins must be consumed daily because any excess leaves your body naturally through urine. Fat-soluble vitamins such as D, E, A and K can be stored in your liver and fatty tissues, but you still need to take in small amounts of each of these vitamins regularly to prevent deficiency.
Vitamin D Deficiency
A 2014 article published in Obesity Reviews states that obese people tend to have lower levels of vitamin D, but it's not yet clear if low vitamin D levels contribute to obesity, or if obesity causes low vitamin D. Regardless, a diet low in vitamin D can cause general tiredness and aches and pains, which could contribute to weight gain by making it difficult to be active and burn off calories. You get Vitamin D from sunlight exposure and dietary sources, which include fish such as swordfish, tuna, and salmon; egg yolks and fortified foods, such as milk, yogurt, orange juices and cereals.
Vitamin B12 Deficiency
Vitamin B12 is naturally found only in foods of animal origin, such as beef, chicken, dairy products and eggs, or in vitamin-fortified foods, such as non-dairy milks and cereals. If you're a vegetarian or vegan, or if you eat meat or dairy products rarely, you could be at risk for a B12-deficiency, which might also raise your risk of obesity. According to a 2013 study published in Medicinski Glasnik, marginal and deficient levels of vitamin B12 were higher in overweight and obese individuals than in the normal-weight group. However it's still not clear if the deficiency causes or is a result of being overweight. A vitamin B12 deficiency may also cause depression and fatigue, which could contribute to weight gain as well.
Vitamin C Deficiency
Although a deficiency in vitamin C might not cause you to gain weight, low vitamin C could be indicative of a poor-quality diet that leads to weight gain. Fruits and vegetables should be your major source of vitamin C, and a diet low in these foods can indicate that your calories may be coming from less nutritious foods, such as fried and processed foods, sodas, and foods high in refined sugar. A 2005 study published in the Journal of Clinical Nutrition found that men and women with a higher waist-to-hip ratio had low levels of vitamin C. Low vitamin C might also cause fatigue, painful joints and decreased immunity.
Next Steps and Precautions
If you have concerns about your weight, you are gaining weight unexpectedly, or you are considering supplementing with individual vitamins, it is best to speak with your medical provider. Your provider can test the levels of vitamins in your body and will be able to tell you if you are deficient. Vitamins have upper level limits and can be dangerous when taken above the suggested amount. Lifestyle and dietary factors may also have an impact on weight, and your doctor may refer you to a specialist or registered dietitian to evaluate your current diet, make recommendations and help determine which nutrients may be lacking.