Estrogen and fat burning
- 06-30-2005, 02:38 AM
Estrogen and fat burning
Nandi posted this over at CEM. Now I wish I wasn't so damn sensitive to estrogen...
I've written extensively about the fat mobilizing and burning properties of estrogen, but up until now (probably for ethical reasons) I've never seen the seemingly definitive experiment carried out: administering estrogen to men and measuring fat oxidation. The study below shows that estrogen increases fat burning and spares glycogen and protein in men.
J Clin Endocrinol Metab. 2005 Jun;90(6):3592-9.
Estrogen supplementation reduces whole body leucine and carbohydrate oxidation and increases lipid oxidation in men during endurance exercise.
Hamadeh MJ, Devries MC, Tarnopolsky MA.
Department of Pediatrics and Medicine, McMaster University Medical Center, 1200 Main Street West, Hamilton, Ontario, Canada L8N 3Z5.
Healthy active men exhibit higher rates of carbohydrate (CHO) and leucine oxidation and lower rates of lipid oxidation compared with their female counterparts both at rest and during moderate intensity endurance exercise. We postulated that this reduced dependence on amino acids as a fuel source in women was due to the female sex hormone estrogen. In a randomized, double-blind, placebo-controlled, cross-over design, we investigated the effect of supplementing 12 recreationally active men with estrogen on whole body substrate oxidation and leucine kinetics at rest and during moderate intensity endurance exercise. Subjects cycled for 90 min at an intensity of 65% maximum O(2) consumption after 8 d of either estrogen supplementation (2 mg 17beta-estradiol/d) or placebo (polycose). After a 2-wk washout period, they repeated the test after 8 d of the alternate treatment. On the test day, after a primed continuous infusion of l-[(13)C]leucine, O(2) consumption, CO(2) production, steady-state breath (13)CO(2), and plasma alpha-[(13)C]ketoisocaproate enrichments were measured at rest and at 60, 75, and 90 min during exercise in the postabsorptive state. Exercise increased energy expenditure more than 5-fold, CHO oxidation more than 6-fold, lipid oxidation more than 4-fold, and leucine oxidation 2.2-fold (all P < 0.0001), whereas it decreased the ratio of lipid to CHO oxidation by 50-70% (P = 0.003) compared with values at rest. Estrogen supplementation decreased respiratory exchange ratio during exercise (P = 0.03). Estrogen supplementation significantly decreased CHO oxidation by 5-16% (P = 0.04) and leucine oxidation by 16% (P = 0.01), whereas it significantly increased lipid oxidation by 22-44% (P = 0.024) at rest and during exercise. We conclude that estrogen influences fuel source selection at rest and during endurance exercise in recreationally active men, characterized by a reduced dependence on amino acids and CHO and an increased reliance on lipids as a fuel source.
- 06-30-2005, 09:15 AM
Hmmm this is interesting and pretty much opposite of the understanding I had of E in men. My total estrogens are below the ref range. I wonder if thats why I have been struggling to get some fat off.
- 06-30-2005, 11:44 PM
This study peaked my interest because it goes against many of the things all of us have learned. I spoke with chemo about it..... The conclusion we had was that men tend to have more muscle, less BF....women tend to be the opposite. Selectively using E to induce metabolic changes could indeed be true as the study above indicates, but we would have to consider how increased E levels effect T levels...and the threshold for E supplementation to avoid negative side effects (Gyno namely). My personal opinion here is that E supplementation is a dumb idea and that there alot more variables that haven't been explored. All in all, a great study...scientific wise... but will we see men using E for fat loss as opposed to steroidals, IGF, GH, T3, clen, and other stims.....highly unlikely
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