Wheat elimination continues to yield explosive and unexpected health benefits.

I initially asked patients in the office to eliminate wheat because I wanted to help them reduce blood sugar and pre-diabetic tendencies.

A patient would come to the office, for example, with a blood sugar of 118 mg/dl (in the pre-diabetic range) and the other phenomena of pre-diabetes or metabolic syndrome (high blood pressure, high inflammation/c-reactive protein, low HDL, high triglycerides, small LDL), and the characteristic wheat belly. Eliminate wheat and, within three months, they lose 30 lbs, blood sugar drops to normal, blood pressure drops, triglycerides drop by several hundred milligrams, HDL goes up, small LDL plummets, c-reactive protein drops.

People also felt better, with flat tummies and more energy. But they also developed benefits I did not anticipate:

--Improved rheumatoid arthritis--I have seen this time and time again. Eliminate wheat and the painful thumbs, fingers, and other joints clear up dramatically. Many former rheumatoid sufferers people tell me that one cracker or pretzel will trigger a painful throbbing reminder that lasts a couple of hours.

--Improved ulcerative colitis--People incapacitated with pain, cramping, and diarrhea of ulcerative colitis (who are negative for the antibodies for celiac disease) can experience marked improvement. I've seen people be able to stop all their nasty colitis medications just by eliminating wheat.

--Reduction or elimination of irritable bowel syndrome

--Reduction or elimination of gastroesophageal reflux

--Better mood--Eliminating wheat makes you happier and experience more stable moods. Just as wheat is responsible for a subset of schizophrenia and bipolar illness (this is fact), and wheat elimination generates dramatic improvement, when you or I eliminate wheat, we also experience a "smoothing" of mood swings.

--Better libido--I'm not sure whether this is a consequence of losing a belly the size of a watermelon or improvement in sex hormones (esp. testosterone) or endothelial responses, but more interest in sex typically develops.

--Better complexion--I'm not entirely sure why, but various rashes will often dissipate, bags under the eyes are reduced, itching in funny p

Track Your Plaque makes Consumer Reports!

8. August 2011 William Davis (27)

. . . but not in a good way.

The September, 2011 issue of Consumer Reports showcases their Protect Your Heart discussion. Third paragraph: "The website Track Your Plaque warns, 'The old tests for heart disease were wrong--dead wrong.' It says heart scans are 'the most important health test you can get.'"

They go on to expose the overuse of heart procedures like angioplasty and stent implantation and offer their advice on how to manage heart disease risk: lower BP, reduce LDL cholesterol, lose weight, stop smoking, take aspirin. They quote Dr. Paul Ridker who declares heart scans are not useful because the "deposits cardiologists worry about are the less stable plaques that CT scans routinely miss."

I thought I'd been transported back to 1995. Not only is it clear that the Consumer Report writers never looked beyond the homepage of Track Your Plaque, but somehow saw our heart disease prevention and reversal program as promoting heart procedures. Incredible.

Of course, the Track Your Plaque program does the exact opposite: Advocates an approach that virtually eliminates the need for procedures and returns control over heart disease to the participant. That's a critical difference.

And, as I've had to remind my colleagues time and time again, what we are really after is an index of total coronary atherosclerotic plaque. Even in 2011, that index remains the simple coronary calcium score, a gauge of total plaque, not just of "hard," stable plaque. Perhaps in 10 years we will be using a better tool to gauge progression and regression of all the components of coronary atherosclerotic plaque, but today it remains the simple, accessible, mammogram-like coronary calcium score.

Consumer Reports does for the idea of heart disease prevention what food manufacturers do for health and weight loss: Echo conventional wisdom of the sort that generally makes us fatter, more diabetic, leads us to more heart procedures and needless deaths. I might use Consumer Reports to rate MP-3 devices or toasters, but I certainly would not rely on them for insightful health advice.

Paging Dr. Basedow

6. August 2011 William Davis (8)

A 23-year old man came to my office having experienced weeks of extreme anxiety, palpitations, and 19 pounds of weight loss triggered by an overactive thyroid.

It all happened because of a large dose of iodine received during a CT scan using iodine-containing x-ray dye. (X-ray dyes are made visible on x-ray due to the iodine content.) This is a reaction first described in the 19th century by German physician, Karl Adolph von Basedow. (Jod is German for iodine.)[caption id="attachment_4313" align="alignleft" width="217" caption="Dr. von Basedow. Image courtesy Wikipedia"]

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Now, here's the kicker: Jod-Basedow only occurs when there is pre-existing iodine deficiency. Indeed, this young man had an enlarged thyroid, signaling longstanding iodine deficiency (a goiter).

This example is among the more flagrant examples of something I have been witnessing: the return of iodine deficiency. As Americans cut back on their intake of iodized salt and fail to obtain iodine in sufficient quantities from seafood, seaweed, or supplementation, goiters and iodine deficiency are making a return in all its glory, reminiscent of the early 20th century, pre-iodized salt.

This young man's frightening experience is yet another way iodine deficiency can show itself, by the overenthusiastic thyroid response to a large dose of iodine when iodine deficiency has been present for a prolonged period.

Iodine deficiency and goiters have been lost to memory for most people. Even the FDA, in its advice for Americans to reduce salt and sodium intake, have forgotten to remind everyone to obtain iodine from an alternative source. "Those who cannot remember the past are condemned to repeat it."

Get your iodine.

Carb counting

5. August 2011 William Davis (20)

In the recent Heart Scan Blog post, Can I eat quinoa, I discussed how non-wheat carbohydrate sources like quinoa, amaranth, black beans, brown rice, fruit, etc. do not exert the inflammation-provoking, appetite-increasing effects of wheat (since gliadin and gluten are not present), nor do they increase blood glucose as enthusiastically as the amylopectin A of wheat--but non-wheat grains can still increase blood sugar quite substantially.

Of course, any food that triggers blood sugar also trigger hepatic de novo lipogenesis, thereby increasing triglyceride levels and postprandial particles (e.g., chylomicron remnants), which, in turn, triggers formation of small LDL particles.

So these non-wheat carbohydrates, or what I call "intermediate carbohydrates" (for lack of a better term; low-glycemic index is falsely reassuring) still trigger all the carbohydrate phenomena of table sugar. Is it possible to obtain the fiber, B-vitamin, flavonoid benefits of these intermediate carbohydrates without triggering the undesirable carbohydrate consequences?

Yes, by using small portions. Small portions are tolerated by most people without triggering all these phenomena. Problem: Individual sensitivity varies widely. One person's perfectly safe portion size is another person's deadly dose. For instance, I've witnessed many extreme differences, such as 1-hour blood sugar after 6 oz unsweetened yogurt of 250 mg/dl in one person, 105 mg/dl in another. So checking 1-hour blood sugars is a confident means of assessing individual sensitivity to carbs.

Some people don't like the idea of checking blood sugars, however. Or, there might be times when it's inconvenient or unavailable. A useful alternative: Count carbohydrate grams. (Count "net" carbohydrate grams, of course, i.e., carbohydrates minus indigestible fiber grams to yield "net" carbs.) Most people can tolerate around 40-50 grams carbohydrates per day and deal with them effectively, provided they are spaced out throughout the day and not all at once. Only the most sensitive, e.g., diabetics, apo E2 people, those with familial hypertriglyceridemia, are intolerant to even this amount and do better with less than 30 grams per day. Then there are the genetically gifted from a carbohydrate perspective, people who can tolerate 50-60 grams, occasionally somewhat more.

People will sometimes say things like "You don't know what the hell you're talking about because I eat 200 grams carbohydrate per day and I'm normal weight and have perfect blood sugar and lipids." As in many things, the crude measures made are falsely reassuring. Glycation, for instance, from postprandial blood sugars of "only" 140 mg/dl--typical after, say, unsweetened oatmeal--still works its unhealthy magic and will lead long-term to cataracts, arthritis, and other conditions.

Humans were not meant to consume an endless supply of readily-digestible carbohydrates. Counting carbohydrates is another way to "tighten up" a carbohydrate restriction.

One hour blood sugar: Key to carbohydrate control and reversing diabetes

2. August 2011 William Davis (27)

Diabetics are instructed to monitor blood glucose first thing in the morning and two hours after eating. This helps determine whether blood sugar is controlled with medications like metformin, Januvia, Byetta injections, or insulin.

But that's not how you use blood sugar to use to prevent or reverse diabetes. Two-hour blood sugars are also of no help in deciding whether you have halted glycation, or glucose modification of proteins the process that leads to cataracts, brittle cartilage and arthritis, oxidation of small LDL particles, atherosclerosis, kidney disease, etc.

So the key is to check one-hour after-eating (postprandial) blood sugars, a time when blood glucose peaks after consumption of carbohydrates. (It may peak somewhat sooner or later, depending on factors such as how much fluid was in the meal; protein, fat, and fiber content; presence of foods like vinegar that slow gastric emptying; the form of carbohydrate such as amylopectin A vs. amylopectin B, amylose, fructose, along with other factors. Once in a while, you might consider constructing your own postprandial glucose curve by doing fingersticks every 15 minutes to determine when your peak occurs.)

I reject the insane notion that after-eating blood sugars of less than 200 mg/dl are acceptable, the value accepted widely as the cutoff for health. Blood sugars this high occurring with any regularity ensure cataracts, arthritis, and all the other consequences of cumulative glycation. I therefore aim to keep one-hour after-eating glucoses 100 mg/dl or less. If you start in a pre-diabetic or diabetic range of, say, 120 mg/dl, then I advise people to not allow blood glucose to go any higher. A pre-meal blood glucose of 120 mg/dl would therefore be followed by an after-eating blood glucose of no higher than 120 mg/dl.

No doubt: This is strict. But people who do this:

--Lose weight from visceral fat
--Heighten insulin sensitivity
--Drop blood pressure
--Drop HbA1c and fasting glucose over time
--Reduce small LDL and other carbohydrate-sensitive measures

By the way, if you inadvertently trigger a high blood sugar like I did when I took my kids to the all-you-can-eat Indian buffet, go for a walk, bike, or burn the sugar off with a 30-minute or longer physical effort. Check your blood sugar again and it should be back in desirable range. But then learn from your lesson: Eliminate or reduce portion size of the culprit carbohydrate food.

Wheat Belly coming to bookstores!

31. July 2011 William Davis (18)

Anyone following the conversations on these pages know that I have some very serious concerns about this thing being sold to us called "wheat"--cause it ain't wheat! It is the result of incredible genetics shenanigans inflicted on this plant, mostly in the name of increased yield per acre.

I now classify wheat as "Public Enemy #1," the prime nutritional culprit underlying obesity, heart disease, "cholesterol" abnormalities, hypertension, arthritis, psychiatric illness, and on and on. Once you read the full story, I believe that you will agree: Modern Triticum aestivum, the plant that now serves as the source for virtually all the wheat flour products now consumed--organic, whole grain, multigrain, sprouted . . . it makes no difference--does not belong in the human diet. So many people, searching for solutions for their fatigue, weight gain, leg edema, incurable rashes, joint pain, etc., will find their answers here.

Wheat Belly: Lose the wheat, lose the weight and find your path back to health will be on bookstore shelves including Barnes and Noble August 30, 2011 or is available for preorder here at Amazon. Wheat Belly will also be available as a downloadable Kindle book and as unabridged audio CDs.

You can also follow the Wheat Belly conversations on my Wheat Belly Blog. One of my recent posts discusses the herbicide-resistant semi-dwarf wheat strain, Clearfield, that is now making its way to more and more supermarket shelves.

You'll also find more conversation on the Wheat Belly Facebook pages.

The exception to low-carb

31. July 2011 William Davis (60)

I witness spectacular results restricting carbohydrates, both in the office as well as in my online experiences, such as those in Track Your Plaque. Of course, the diet I advocate is not just low-carb; it starts with elimination of wheat (for a long list of reasons). So the diet is wheat-free in the setting of low-carbohydrate.

What does this accomplish? Here's a partial list:

--Weight loss-Specifically, loss of visceral fat, the kind hinted at on the surface as "love handles" or what I call "wheat belly."
--Reduced blood sugar and HbA1c (reflecting prior 60-90 days glucose)
--Marked reduction in small LDL and triglycerides, increased HDL
--Reduced inflammatory measures like c-reactive protein
--Reduced leptin and leptin resistance, increased adiponectin
--Reduced estrogen aing typically follows the aborted attempt.

Fasting cannot work as long as the 2-hour cycle of hunger continues. The first step: Eliminate the 2-hour cycle of hunger by dramatically reducing or eliminating carbohydrates. Our preferred method is to eliminate wheat, cornstarch, and sugars. (Just be aware of wheat withdrawal, the fatigue that develops in the first 5 days after wheat elimination that affects up to 30% of people.)

Once wheat, cornstarch, and sugars are eliminated, hunger reverts to that of physiologic need--appetite will be smaller and less intense, since it is driven by your body's needs, not by abnormal stimulation from wheat, cornstarch, and sugar. The fear of not having food dissolves, the 2-hour cycle of mental fogginess, fatigue, and hunger will be gone.

Intermittent fasting is a wonderful strategy for reducing weight; gaining control over lipids, lipoproteins, and coronary plaque; regaining appreciation for food; reducing appetite. But it's not even worth trying unless you've already eliminated the unnatural appetite triggers that will booby-trap any fasting effort.

Test your own thyroid

7. September 2009 William Davis (15)

134 people responded to the latest Heart Scan Blog poll:

When I ask my doctor to test my thyroid, he/she:

Accommodates me without question 45 (33%)

Questions why, but orders the tests 49 (36%)

Refuses because you seem "healthy" 20 (14%)

Refuses without explanation 4 (2%)

Ridicules your request 16 (11%)

That's better than I anticipated: 69% of physicians complied with this small request. After all, you're not asking for major surgery. You're just asking for a very basic test, as basic as a blood count or electrolytes. 36% of respondents said that their doctor asked why, but still complied; this is simply practicing good medicine--If there is a problem, your doctor would like to know about it.

However, the remainder--31%--were refused in one way or another. Incredibly, 11% were ridiculed.

Although this was not asked in the poll, I believe that it is a safe assumption that you asked with good reason: you're abnormally fatigued, you have been gaining weight for no apparent reason or can't lose weight despite substantial effort, or you feel cold at inappropriate times.

Let's say you're tired. Ever since last summer, you've suffered a gradual decline in energy.

So you ask your doctor to assess your thyroid. He refuses. "You're just fine! There's nothing wrong with you."

You disagree. In fact, you are quite convinced that there is something physically wrong. What do you do?

You could:

--Drink more coffee
--Exercise more in the hopes that it will snap you out of your lethargy
--Sleep more
--Take stimulants of various sorts

Or, you could get your thyroid assessed and settle the issue. But how can you get this done when your doctor won't accommodate you, even though you have perfectly fine health insurance and are simply interested in feeling better and preserving your health?

You could test your thyroid yourself. This is why we're making self-testing kits available. Test kits are available here.

This is yet another facet of the powerful revolution that is emerging: Self-directed health.

Trains, planes, and heart scans

4. September 2009 William Davis (10)

A Heart Scan Blog reader posted the following question:

It is not clear to me why getting a cardiac scan is the necessary first step, if in fact the next step would be to bring down small LDL particles which is revealed on a NMR lipoprofile or VAP test. Why isn't the NMR or VAP test the first thing?

Good question. Think of it this way:

Lipoproteins, as measured via VAP (Vertical Auto Profile) or NMR (Nuclear Magnetic Resonance), provide a snapshot of risk from a metabolic viewpoint at that moment. Lipoproteins shift with the tides of age, menopause, weight changes, even what you ate last evening for dinner (especially small LDL). There are also other factors that cause coronary plaque, as well, not revealed through lipoprotein testing, such as vitamin D deficiency, smoking, high blood pressure, phosopholipase A2, lipoprotein(a), inflammatory factors, thyroid dysfunction, omega-3 fatty acid deficiency, etc.

A heart scan, providing a coronary calcium score, provides an indirect measure of coronary plaque that is the sum total of lipoprotein and other plaque-causing factors that have accumulated up to the time of your scan--regardless of the cause.

It means that two females, each 60 years old, with 70% small LDL, HDL 42 mg/dl, triglycerides 150 mg/dl, and mild hypertension, have identical markers for potential coronary risk, but can have widely different heart scan scores. One might have a score of zero, while the other might have a score of 300.

Why would the same panel of causes measured at one moment yield wildly different quantities of plaque? Several reasons:

1) The lifestyles, eating habits, and weight of each woman differed during their earlier years, not currently reflected in this moment's lipid or lipoprotein patterns. Perhpaps one experienced several years of extraordinary stress from a failed marriage, or suffered through two years of depression that caused her to smoke and overeat.

2) There are hidden factors that affect coronary plaque growth that we are presently not able to detect, e.g., vitamin D receptor genotype, cholesteryl-ester transfer protein variants, variation in inflammatory factors. If we can't measure it, we won't know whether it might influence coronary plaque risk.

With all the changes that occur over a person's life, with the uncertainties of yet-to-be-identified causes for coronary plaque, how can you possible know what your risk for heart disease truly is? Yup--a heart scan. Do it and you will know.

D2 and D3 are two different things

3. September 2009 William Davis (15)

Helena posted this instructive comment in response to the Heart Scan Blog post, Weight loss and vitamin D. It illustrates the confusion common among physicians and pharmacists on the differences between D2 and D3.

(Edited slightly for clarity.)

Not many weeks ago a colleague of mine (let’s call him Eric) asked me if I knew the difference between D2 and D3 and I told Eric that D2 comes from irradiated mushrooms and D3 comes from wool. In other words, D3 is the same kind of vitamin as humans get from the sun. Humans just don’t get enough and we can’t produce it on our own, like the sheep can. (D3 is natural for humans, D2 is not.)

After telling Eric this, he asked me how he would know what he is taking and I gave him the medical definitions of them both (D2 = Ergocalciferol; D3 = Cholecaliciferol). Since I was aware that he had gotten his Vitamin D by prescription, I told him “I am 99.9% sure that you are taking D2, but I would be thrilled to find out I am wrong.”

Eric called his pharmacy right away and got the answer I was expecting: ergocalciferol. On confronting the person Eric was talking to, the answer he got back was that Ergocalciferol is the only Vitamin D they are giving out.

A week later, Eric had a new appointment with his doctor and decided to ask him about the D2/D3 issue. The doctor said he knew that there was a difference in them both, but could not say what, not even the basic facts I mentioned above. But the doctor stamped a post-it with what he had sent to the pharmacy just to show Eric. “Vitamin D3; 50,000IU tab” is what the stamp said.

Eric, off course, got confused and was starting to believe that the pharmacy had made a mistake by giving him Ergocalciferol (D2) since the doctor had given him D3, or at least that is what was stamped on the little note he had.

Today, after getting a refill of his Vitamin D he also got and kept all his paperwork that came along with it. Still believing that stamp the doctor had given Eric earlier, he asked me to double and triple check that my definition of D2 and D3 was correct. I did, just for my own sanity, and I was still right.

One of the sheets Eric brought me today was the “Patient Education Monograph” sheet stating the drugs and how to use it and so on. The thing that jumped out the most to me was this:

Generic Name: Vitamin D – Oral
Common Brand name(s): Drisdol, Maximum D3
Identification: PA140 Green Oval Capsule

This is the Drug Eric was given: Vitamin D 1.25 MG softgel; Generic name: Ergocalciferol

My researching mind went into high concentration mood and I started to dig. And this is what I found:

The brand name Drisdol is Ergocalciferol (D2), not D3. The Brand name Maximum D3 seems to be hard to find out there in cyber space as a brand name. But the ones I found that were called Maximum D3 seems to be the real stuff, however none of them required a prescription.

When trying to find out through the identification number on the pills (PA140) I now know for sure that Eric is taking Vitamin D2 and not the preferred Vitamin D3. The brand name, Drisdol, had the identification W on one side and D92 on the other, but it is still Ergocalciferol.

The only conclusion I can draw from all this is that the medical industry does not know or care about the difference in D2 and D3 – it is all same to them. And as long as the pharmacies only give out D2 it does not matter what the doctor prescribe anyway.

I know that people are most likely to be prescribed a D2 pill than to be told to buy over-the-counter D3. But it was almost heart breaking to see the letter D and number 3 right next to the drug Drisdol, as we know is a D2 vitamin. It just didn’t make sense to me that they can be labeled as the same type of medication, when we know it is not!

Incredible.

Why prescribe plant form D2 when you can get perfectly reliable, safe, effective D3--the human form, at the health food store for about $6?

Once again, it's the peculiar false bias of physicians and pharmacists: If it's prescription, it must be good; if it comes from a health food store, it must be bogus.

Humans need human vitamin D. Plain and simple.

For more on the D2 vs. D3 issue, see the Heart Scan Post, The case against vitamin D2.

Weight loss: Different causes, different solutions

1. September 2009 William Davis (8)

Heart Scan Blog reader, Kris, related this enlightening story of weight loss (slightly edited for clarity).

Kris learned that excess weight is gained through multiple causes. The solutions are therefore multiple, not just one change in diet or two.

I started studying about my thyroid issue much earlier and did lose some weight. But ever since I started following Dr. Davis’s blog, it has given me confidence that I was on the right track. I did have my thyroid and iodine figured out from other sources, but Dr. Davis helped me to understand the issues with not only the thyroid but vitamin D3, fructose, fish oil, niacin, wheat etc. I have lost 43lb in last 14 months.

It seems to me that there are certain percentages of weight connected with different issues. For example, after I gave up alcohol and sugar, I lost about 14lbs from total weight of 243lbs, weight came down to about 229lb. Then it stopped at 229lb, even though I was in the gym almost 5 to 6 days a week with full workouts.

After I changed my thyroid medication to natural thyroid hormones (took synthetic T4 for over 10 years), the weight dropped down further 13lbs or so in matter of few days, shape of the face changed from moon shape/double chin to ordinary long face. Then it kind of stopped at around 213-216 lbs.

After giving up wheat, reducing carbs, increasing protein intake (whey protein, chicken etc. no soya, no fructose) the weight came down another 14lbs. Now it is around 200-202lbs and I am over 6.2 tall with heavy set of bones.

I feel better than I have ever in my life. More stamina, more clarity/no fog, more confidence and 99% of the time relaxed and being able to see the situation from multiple angles.

I use to be able to drink a liter or more jack denial without a problem in one evening but now can’t stand half a can of beer (I miss JD). Drinking alcohol makes me sick. I sleep well and if I wake up in the middle of the night, I have no problem going back to sleep. No more out of breath stair climbing at all.

One other thing: I used to be the most attractive meal to the mosquitoes, but not anymore. This year I haven’t been bitten once. I take my dog to the park everyday and I do not use any mosquito repellent, what a relief. I don’t know if it is because of thyroid, iodine, wheat or something else. Skin texture has changed dramatically. I do not use full soap or shampoo, 20% borax, 10 percent of my soap or shampoo for scent and rest water, mixed in a 500ml bottle. No more dandruff, dry skin, pimples for me.

Dr. Davis I am thankful to people like you who have the ability to see beyond what you have been taught and have the guts to say the way it is. Most of us work to make living on daily basis but some make their living while spreading their knowledge to save lives. Dr Davis you are one of those few people. Please keep it going.

Calling all losers!

29. August 2009 William Davis (14)

I'd like to invite anyone who has followed the Track Your Plaque Break the Weight Barrier program to consider posting their stories and photos on the Heart Scan Blog.

Because our focus is prevention and reversal of coronary heart disease, we have not made an effort to catalog the weight loss experience that people have while on the program. For many, weight loss has been substantial. (Several people this week alone have reported weight loss of 9 to 46 lbs in the past 6 months.)

It would be helpful to hear and see these results.

For those of you who don't mind having a story and photo on this Blog, please come back in future to post your results. You will find this post by entering "weight loss" into the site-specific search bar at the top of the page.

Weight loss and vitamin D

28. August 2009 William Davis (28)

At the start of her program, Penny's 25-hydroxy vitamin D blood level showed the usual deficiency at 22 ng/ml.

She supplemented with 8000 units of vitamin D. Another 25-hydroxy vitamin D blood level several months later showed a level of 67.8 ng/ml, right on target.

But Penny also began our diet, including the elimination of wheat, cornstarch, and sugars, and, over 6 months, lost 34 lbs.

Now a much trimmer 146 lbs (still more to go!), another vitamin D blood level: 111 ng/ml.

Penny's weight loss means that the vitamin D is distributed in a smaller total volume, particularly a lower volume of fat.

This is a common phenomenon with substantial weight loss: lose weight and the need for vitamin D is reduced. The reduction in dose is roughly proportion to the weight lost. Vitamin D should therefore be reassessed with any substantial change in weight of, say, 10 lbs or more, either up or down, because of the influence of fat on vitamin D blood levels.

Some references on this effect:

Men and women over age 65:
Adiposity in relation to vitamin D status and parathyroid hormone levels: a population-based study in older men and women.

Obese women:
Low 25-hydroxyvitamin D concentrations in obese women: their clinical significance and relationship with anthropometric and body composition variables

Obese children:
Hypovitaminosis D in obese children and adolescents: relationship with adiposity, insulin sensitivity, ethnicity, and season.

African-Americans:
Relationship of vitamin D and parathyroid hormone to obesity and body composition in African Americans.

Although the bulk of the effect is most likely due to sequestration by fatty tissue, perhaps less sun exposure in obese people also contributes:
Body mass index determines sunbathing habits: implications on vitamin D levels.