Allegedly 'Harmless' Thyroid-Based Fat Burner 3,5-T2 Works Like a Charm, While Commonly Sold 3,3-T2 Could Mess W/ Your Blood Glucose Levels, Liver & Body Fat + Muscle

These are the kind of abs, you will see on products with T2 and/or T2 and other alleged fat-burners. Don't be fooled by the ads - even if it's the actually active form of diiodothyronine (T2), namely 3,5-T2, you're buying, the pills alone won't get you to the sub-10% body fat range you  may be dreaming of.

I've written about the thyroid hormone metabolite diiodothyronine aka T2 before. Accordingly, you will probably know that it has long been thought of as an inactive byproduct of the thyroid hormone metabolism (read previous T2-articles). You will also be aware of the fact that research shows that (a) this is not the case and that (b) only one of its two forms, namely 3,5-diiodothyronine (3,5-T2) shares the fat burning, metabolic effects of its big brother triiodothyronine aka T3.

Just like me, you probably don't know, however, why supplement companies are still stupid enough to use both 3,5- and 3,3-diiodothyronine in their allegedly fat burning supplements - "stupid", because we already knew it has no effect and even more stupid, since a recent study from the Universidade de São Paulo and the Houston Methodist Research Institute has shown that it will, in total contrast to 3,5-T2, of which the latest research by da Silva Teixeira et al. shows that it will reduce the blood glucose levels independently of insulin sensitization, impair the metabolism of glucose.

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Yes, you read that right: While 3,5-T2 burns fat (especially in the liver) and increases your metabolism, its cousin 3,3-T2 will do nothing for your BMR/RMR + glucose and fatty acid metabolism and can, on top of that, even impair your glucose metabolism and, as the data in Figure 1 shows, increase the amount of liver fat and food intake.

Figure 1: Effects of T3 (DT3 at 0.75 mg/kg), 3,5-T2 (D3,5-T2 at 1.25 and 12.5 mg/kg) and 3,3 T2 (D3,3-T2 at 1,25 mg/kg) on (A) body weight trajectory, (B) body fat (%), lean mass (%), (D) body temperature, (E) food intake, (F) liver fat, (G) heart weight & (H) TSH of diet-induced obese mice (da Silva Teixeira. 2016).

I guess this negative effect on your glucose metabolism alone should be reason enough to avoid supplements with the commonly used combination of 3,3- and 3,5-T2.

In man, there's a J-shaped correlation between blood glucose 3,5-T2 in (open boxes: all subjects; closed boxes: euthyroid patients), but no significant correlation with waist circumference (a proxy of visceral fat) and subcutaneous fat according to Pietzner et al. (2015).

What dosages are we talking about? Unfortunately, the study at hand provides no guideline as to how much of this thyroid metabolite is actually necessary to boost your overall, fat and glucose metabolism, because the regular way to calculate human equivalent doses (HED | learn how to do it) seems to be way off when we talk about thyroid hormones. Humans appear to need much lower doses of exogenous thyroid hormones to see the same effects as rodents; and the dose regimen that delivered the most significant effect in the study at hand would translate to hilariously high doses of 3,5-T2 - doses you can luckily (?) never get out of any of the T2-supplements on the market).

Plus: The fact that a 2015 study by Pietzner et al. suggests that, in healthy euthyroid human beings, there's a J-shaped correlation of circulating 3,5-T2 levels and glucose (p >> 0.05 for insulin, waist, and subc. fat) with the latter being more or less constant until a certain optimal 3,5-T2 level is achieved and the fasting glucose levels "explode" (see Figure to the left).

After all, you can only hope for the 3,5-T2 the Brazilian scientists who have been dabbling with diiodothyronines in previous studies, already, to counter the ill effects of 3,3-diiodothyronine (3,3-T2).

Figure 2: (A) Fasting blood glucose, (B) glucose response during glucose tolerance test and (B) insulin levels in diet-induced obese mice according to treatment (da Silva Teixeira. 2016).

What's more, no supplement company can give you a guarantee that the 3,5-T3 in their products will fully counter the ill effects of 3,3-T2 on liver fat, the response to glucose tolerance tests, and the increased levels of insulin and appetite you can see in Figure 2 (and Figure 1, respectively) - no matter, how large the words "synergy" or "synergistically" are plastered all over the supplement bottle.

Read before using T2-products: "High-Dose 3,5-Diiodo-L-Thyronine (T2) Has Similar Side Effects as Regular Thyroid Hormones: Natural Thyroid Hormone Production ↓, Myocardial Stress ↑, Heart Weight ↑" | more.

So what's the verdict then: If you have understood that neither form of T2 is free of side effects (see "High-Dose 3,5-T2 Has Similar Sides as Regular Thyroid Hormones" | read it) and still want to use a T2-product, you better make sure it contains only the actually active 3,5-diiodothyronine (3,5-T2) and no 3,3-diiodothyronine) stupid supplement producers have put into the product to be able to claim that they would thus make sure to keep the side-effects at bay.

With a 3,5-T2 product you could at least hope for (a) weight loss / the prevention of weight gain, (b) fat loss and thus increases in relative lean mass, and, as the study at hand demonstrates (c) reduced liver fat and improved glucose tolerance and fasting glucose as well as insulin levels... all that, however, requires the product to be high-dosed - probably higher than the average fat burner you can buy at your favorite supplement shop (see red box for more information on the dosing regimen) | Comment!.

References:

• Pietzner, Maik, et al. "Translating pharmacological findings from hypothyroid rodents to euthyroid humans: is there a functional role of endogenous 3, 5-T2?." Thyroid 25.2 (2015): 188-197.