Having a RAVENOUS appetite (or conversely no appetite at all - anorexia) and unintended weight loss are symptoms of early thiamine deficiency.   People who are physically active, athletes, physical laborers, those who exercise outside regularly have a higher metabolic need for thiamine.  Exercising outside regularly can cause more thiamine loss because sunlight breaks down thiamine.  (This is why people with heat stroke are administered thiamine.)  More thiamine is lost through the kidneys in those who exercise regularly.  Because blood tests for thiamine deficiency is so inaccurate, the World Health Organization suggests, if thiamine deficiency is suspected, give thiamine and look for health improvement.   Do not take Thiamine Mononitrate as this form is not well absorbed nor utilized in the body.  It is frequently found in foods, and multivitamins and B1 supplements because it will not break down with exposure to light while sitting on a shelf at the store.  Thiamine Mononitrate is shelf stable - it won't break down with light exposure - and this makes it not bioavailable.  The body only absorbs about 30% and utilizes less than that because it's so hard to break down.   Benfotiamine and the form of thiamine called TTFD (Tetrahydrofurfuryl Disulfide) and thiamine hydrochloride are wonderful forms to take.   I'm familiar with these symptoms because I dropped sixty pounds in a month because I had developed thiamine deficiency.  I ate well, exercised, and took a multivitamin (with thiamine Mononitrate), but the metabolic needs of my body demanded more.  The years of poor absorption due to undiagnosed Celiac disease had depleted my stores of thiamine.  My doctors did not recognize thiamine deficiency symptoms, even when they progressed to Wernicke's Encephalopathy.  They said I was making things up and sent me home. With nothing else to lose (I could feel myself dying), I took high dose thiamine hydrochloride as the WHO suggested and had improvement within the hour.   I also tried Benfotiamine and TTFD in the months that followed and had even more significant health improvement. Please don't wait until your brain starts malfunctioning or other organs start failing.  Please take thiamine soon.  It's nontoxic and safe even in high doses.  Thiamine works with other B vitamins, especially Riboflavin and Pyridoxine, so supplementing with a B Complex is essential as well.  Magnesium is needed as well to make life sustaining enzymes. There's no harm, no foul in trying Thiamine.  If for no other reason than to prove it is not thiamine deficiency.   P. S.  Thiamine is needed to turn on Vitamin D, turning it into its active form.  Otherwise  Vitamin D can't be utilized and just builds up in the system.

In fact, funny idea, my partner suggested I shld model for the over 50s section, and do it now b4 I start piling on the pounds - if only that would happen! It is over a year now... I am 48kg and should be 54-55, that was my wooonderful Perfect weight before....:( Nothing lasts for ever, as the song goes... To those out there who have a little more rather then less fat on them - celebrate it! Is Healthy!  

Oh and yes, thanks, other than being permanently RAVENOUS and not yet putting on weight, I am feeling pretty good. I jog, do yoga, today cycled 12km to a food market then to another place to get my fish, then my gluten-free bread... My life is All about food!;( But I shld prob. be less active as obv is keeping the pounds off... And having some muscle makes me feel less depressed with my skeletal appearance.

A big Thank you! To all who replied. V informative and interesting. Re VitD, mine was always good, between 60 and 70. Then on the Bone Support Supplements by Natures Plus it jumped to 90, 110 and then over that! I was getting to be VitD toxic... As the supps had 25mcg VitD, which was obviously enough to tip me over... I always go out with shorts whwnever the sun pops out to make sure I get it naturally. They say the activated form of D3 ie. Cholecalciferol is used as the strongest rat poison that exists! I also only eat wild caught salmon, only organic, no sugar, bad fats etc etc.... In fact I am 50 yet people think am 35 and am sure is partly genetic but mostly diet(!). But is Not helpful when I need my GP to take my issues seriously.  Interesting about the oestrogen theory! Will research further, thanks! And thank you to you who suggested the thiamine B1 deficiency, it is only a small possibility as I have Loads of B1 in my diet, but is an interesting theory and thiaminase is smthg I will look into! Also thank you to the London person who sent me a VitA test link. I was told these home kits are not worth thr money;( In fact I plan to go abroad where you get every micro and macronutrient as well as all minerals and vita checked for 350euros! Is absolutely crazy London has nothing like that. I did a hair mineral test here, which was interesting, and even that they send off to a lab in Florida!

@Celiac50, Other than finding foods that make your tummy happy, are you feeling well?  No other symptoms?  That's great progress! You don't mention vitamin D status.  Vitamin D deficiency in the UK has been estimated to be as high as 60% of the population. Celiac Disease causes depleted oral vitamin D from malabsorption.  Most people do not get enough UV light to activate skin creation of vitamin D. Vitamin D supplementation in the United Kingdom: time for change Vitamin D Is Not as Toxic as Was Once Thought It looks like you are going to have to try changing out food by food, until you find the one.  Start with the supplements.      Wild caught vs. farm raised?  Sometimes it is just a subtIe change that can do it. I know that switching to grass fed milk has been good for me.