Vit D and Weight Loss
clipped from http://www.womentowomen.com/healthynutrition/vitamind.aspx 
I’m sure many of you have seen the “diet with dairy” ads launched by the American Dairy Council. Some studies have shown that weight loss does occur with an increase in calcium intake, while others appear to refute this. Since vitamin D is directly involved in calcium absorption, it stands to reason that vitamin D is also a factor in how the body regulates weight.
Moreover, people who have a reduced capacity to mobilize vitamin D often weigh more and have more body fat than those with full capacity. In the past 20 years multiple studies have shown a correlation between higher blood levels of vitamin D and leaner body mass.
To my thinking, what seems essential for us to understand here is the vitamin D connection with insulin resistance. Vitamin D deficiency may contribute to the wide set of disorders associated with metabolic syndrome (syndrome X), as well as to PCOS. In a study published in 2004, the authors saw a 60% improvement in insulin sensitivity in healthy, vitamin D replete adults — and concluded vitamin D was more potent than two prescription medications commonly used to treat type 2 diabetes! But the cadres of drug reps spread out across America are not likely to be reminding your healthcare practitioner about this study. They are not likely to have heard about it!
Clearly, vitamin D seems to be very important in regulating our weight, but we don’t yet understand the mechanism involved or how it relates to our environment and individual biochemistry. Still, there seems to be a correlation between rising rates of obesity and vitamin D deficiency. If you are having difficulty with insulin resistance or weight gain — or can’t keep the pounds off once you lose them — you may want to have your vitamin D levels checked by your healthcare practitioner.
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Fat Loss Nutrition Blog
http://www.fatlossnutrition.com/blog/2008/vitamin-d-increases-weight-loss/ 
Interpreted research on fat loss nutrition and exercise.
Vitamin D Increases Weight Loss
March 17th, 2008 | by David Spelts |
Supplementing with vitamin D can increase the rate of weight loss during dieting.  Those with high blood levels of vitamin D achieved triple the weight loss of those with low levels of the vitamin.
The groups received either a high vegetable diet or a high cereal grain diet.  Both groups lost weight, but the effect of vitamin D was only achieved in the high cereal grain diet… indicating that at least part of the benefit results from improved insulin sensitivity.
Optimal vitamin D levels can only be achieved through supplementation or sun exposure.

PMID: 18279549
      8 Responses to “Vitamin D Increases Weight Loss”
   3.    By Milton Hare on Mar 31, 2008 | Reply
      I HAVE OBSERVED THAT DAILY VITAMIN D3 4,000 IU + 1000 MG CALCIUM DOES IN FACT FREQUENTLY TRIGGER WEIGHT LOSS IN INDIVIDUALS WITH AN AUTO-IMMUNE DISEASE
      I am commenting about this brief note of an unnamed study suggesting that weight loss is triggered at least in some individuals by calcium and Vitamin D3 (cholecalciferol). I am not a doctor or a researcher. For the past two years I have been generally suggesting that individuals healthy or unhealthy take a daily dose of 2,000-4,000 iu of Vitamin D3, and the standard daily minimum combination of calcium, magnesium and zinc available at any pharmacy or supermarket containing contains 1000 mg of calcium to individuals with various auto-immune diseases. To my initial surprise, individuals with auto-immune diseases like rheumatoid arthritis, high blood pressure, Type II diabetes, COPD and multiple sclerosis have experienced the loss of forty to fifty pounds of fat within six months of taking this daily dose with no apparent side-effects. This fat loss is always accompanied by a perceived reduction in auto-immune symptoms – lower blood pressure, higher insulin sensitivity, improved lung function with COPD, lessened pain and better mobility with rheumatoid arthritis. Also, many of these individuals have noted much higher energy levels and improved muscle and skin tone. Note that the 2,000 to 4,000 iu daily dose of D3 is five to ten times higher than the 400 iu RDA for Vitamin D3 for mature adults. I have not observed similar weight loss in individuals who do not have active auto-immune symptoms. This suggests to me that some weight gain may be a symptom of auto-immune disease rather than a consequence. I also have not noticed similar effects when the Vitamin D3 dose is 400 or 800 iu daily as for one year previous I recommended taking a multiple vitamin and a single 400 iu pill. Several individuals promptly began losing weight when they raised their daily dose from 400 or 800 iu to 2,000 iu (one pill) or 2,400 iu (one 2000 iu pill and a multiple vitamin containing 400 iu). This is observational data, not research, but an individual with an auto-immune disease would not raise eyebrows at the Food and Drug Administration (FDA) if they took a daily dose of 2,000 iu D3, 1000 mg of calcium, 500 mg of magnesium and 10 to 15 mg of zinc.
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   9.   By Gina on Nov 29, 2009 | Reply

      I found your post after doing an ask.com search for link between Vitamin D and weight loss. I have APLS and Celiac. I am stable for APLS on coumadin, which thankfully, I tolerate well. I have been GF for 5+ years. I initially lost a good 15 pounds when first I started on GF diet. Since then I have been fairly stable, waffeling between 163 -168 (upper limit of my normal BMI.) I noticed that my weight went up every winter and down every summer. I also noticed that even though I hike more in the summer, my osteoarthritis is much worse in the winter. I have taken supplements but Vitamin D is on that “avoid if on coumadin” list.
      This year I began in first of Nov. to go to a tanning bed for brief sessions — 12 minutes, twice a week. No arthritis pain — in fact I have more flexibility then I’ve had in years. And my weight has dropped all month. I am now down to 160 — and still dropping about .5 pound a week. My metabolism remains high, I have gobs of energy, my stomach growls constantly — despite eating like a pig.
      I don’t have much of a tan yet — you have to scrutinize the underwear lines to see the color change — but I feel great! Just 5 years ago I thought I’d never walk up and down stairs without clinging to the bannister while in great pain. Now I hop, skip and jump — and look — No hands Ma! I don’t care about the tan — but the freedom from joint pain and the energy burst — WONDERFUL!