Everyone knows that vitamin D is essential for healthy bones, but the latest research shows that it may be a big factor in weight loss and weight management. Why? Well there seems to be a connection between low levels of vitamin D and insulin resistance. (Insulin resistance is the term used for when the body can make insulin, however cannot use it properly to convert glucose into energy. Thus the body holds on to it and stores it as fat)

Vitamin D deficiency is common in adults. One of the reasons is because we're stuck in offices all day instead of getting some much needed sunlight. Natural sunshine has an abundance of vitamin D. Also as we age, our bodies slowly lose the ability to mobilize vitamin D.

Are you vitamin D deficient? The best way to know for sure is to get your levels checked by your doc. But besides weight gain (or having trouble losing weight) here are some symptoms of vitamin D deficiency: Muscle pain, weak bones/fractures, low energy & fatigue, lowered immunity (get sick a lot), symptoms of depression or mood swings, sleep irregularities, IBS

Marcelle Pick an OB/GYN NP has the following advice to prevent vitamin D deficiency

What You Can Do To Prevent Vitamin D Deficiency

Vitamin D deficiency may be a pervasive problem — one that we treat with specific therapies at our medical practice — but the best way to protect yourself from any deficiency is to build your health from the bottom up and let your body balance itself. We acknowledge the controversy over whether our primary source of vitamin D should be the sun, diet, or supplements. Which combination is best for you depends on many variables, including your age, nutritional status, and geographic location. In a world where so many of us are at risk of vitamin D deficiency, we recognize each of these sources as valuable. With this in mind we recommend the following steps to prevent vitamin D deficiency:

Allow yourself limited, unprotected sun exposure in the early morning and late afternoon (no more than 15 minutes for light-skinned individuals, 40 minutes for darker skin)
Eat a diet rich in whole foods. Nutrient-dense, fatty fish like mackerel and sardines are good sources of vitamin D. Egg yolks, fortified organic milk and other dairy products, and some organ meats (like liver) are also reasonably good natural sources of D. Because vitamin D is still somewhat of a mystery, we’re not sure which co-factors are important for its absorption, but we can surmise they are most fully present in wholesome food.
Take a top-quality multivitamin every day to fill in any nutritional gaps, preferably one that includes fish oil.
Take a vitamin D supplement. Supplement additionally with vitamin D3 at 1000–2000 IU daily if you do not get testing (or higher with testing, under the care of your healthcare practitioner). For a long time, vitamin D therapy was being prescribed as vitamin D2. To our thinking, this form has more potential for toxicity and is much less effective than natural vitamin D3. Nowadays vitamin D3 supplements are widely recognized as the superior, more bio-ready form for use in the body. How much you need really depends on your particular needs, so testing is really the best way to go for most people.
Check with your healthcare professional about vitamin D testing. If you think you may be suffering from vitamin D deficiency, get a blood test and ask for the results. I like to see an optimal value of 50–70 ng/mL. A conventional doctor might think anywhere from 20–50 ng/mL is normal, but that recommendation will soon change as the newest research becomes incorporated into the standard of conventional care.
Discuss adding a vitamin D supplement to your diet with your healthcare provider. If you don’t get out in the sun every day for 15 minutes in the early morning and late afternoon, consider supplementing with 1000–2000 IU per day — at least during the winter months! But you may need higher levels to reap all the long-term health benefits vitamin D has to offer you, so talk it over with your healthcare provider. This is so important for women of all ages — especially those over 50. Then be sure to get follow-up testing to monitor your response.