|Fructose as an injectable Dieting Aid? Sounds crazy, but it works!|
Well, honestly, me neither and if we take a closer look at the experimental design of a 1986 study by Robert A. Gelfand and Robert S. Sherwin from the prestigious Yale University, we will have to relativize the aforementioned claim. Coke alone may not do the trick. Pure fructose, if it's infused right into the bloodstream, on the other hand will "abolishes the entire hormone-substrate response to fasting, and spares body protein without raising insulin above postabsorptive levels." (Gelfand. 1986)
Before we are pondering the results, let's first have a closer look at the actual design of a study was conducted to "examine the influence of low-dose fructose infusion on nitrogen economy and the metabolic response to fasting in man" (Gelfand. 1986 | I know that you should do that in "man", not rodents, but that's costly and has the aforementioned limitations).
To this ends, the aforementioned overweight to obese women who were not diabetic and normal blood glucose and insulin levels, had normal thyroid and liver function and had been consuming a weight maintenance diet with at least 200g of carbohydrates per day before they were recruited for the study, were fasted for a period of 10 days (they did get a multivitamin, a folic acid and a potassium chloride tablet to eat, though ;-) and randomly divided into 2 groups using a crossover design:
- Group 1 (n = 4) received intravenous fructose during the last 3 days of the IO-day fasting period, while
- Group 2 (n = 3) received fructose for the initial 7 days of the fast
|Figure 1: Changes in plasma glucose and insulin (left) and active thyroid hormone T3 (right) during the fast with and without fructose (Gelfand. 1986)|
Hormonal changes and real world effects!
Now hormonal changes are one thing. Real world effects which cannot always be predicted solely by endocrine parameters are yet often a whole different animal. What you would maybe have expected, though, is the decrease in ketone production during the supplement phases, which are indicative of "less starvation" (Blood beta-hydroxybutyrate is only a sign positive ketosis, when you actually eat tons of fat, not when you fast - in that case they are a starvation response; see Table 1)?
|Table 1: Inhibitory Effect of Fructose on Starvation-Induced Ketosis. FFA Elevation, |
Acidosis. and Hyperuricemia (Gelfand. 1986)
|Figure 2: Urinary ammonium loss with sodium bicarbonate (G2) or potassium + calcium carbonate (G3) vs. no buffer (G1) on a 93g all protein starvation diet (Gougeon-Reyburn. 1991)|
One of the factors that contributes to the "reduced rate of energy expenditure" is the the previously mentioned decline in thyroid hormone levels, of which you've just learned that it can be ameliorated by fructose injections (see Figure 1). Another one that is partly related to the decline in T3 is the loss of muscle mass - a process of which Byerley et al. (1996) argue showed that it does not have the protein sparing effects many people believe it would have.
|Figure 3: Fructose decreases the total urinary nitrogen loss by ~40% (Gelfand. 1986).|
- Byerley, L. O., and D. Heber. "Metabolic effects of triiodothyronine replacement during fasting in obese subjects." The Journal of Clinical Endocrinology & Metabolism 81.3 (1996): 968-976.
- Gelfand, Robert A., and Robert S. Sherwin. "Nitrogen conservation in starvation revisited: Protein sparing with intravenous fructose." Metabolism 35.1 (1986): 37-44.
- Gougeon-Reyburn, Réjeanne, François Larivière, And Errol B. Marliss. "Effects Of Bicarbonate Supplementation On Urinary Mineral Excretion During Very Low Energy Diets." The American Journal Of The Medical Sciences 302.2 (1991): 67-74.
- Nakagawa, Takahiko, et al. "A causal role for uric acid in fructose-induced metabolic syndrome." American Journal of Physiology-Renal Physiology 290.3 (2006): F625-F631.
- Ravussin, Eric, et al. "Reduced rate of energy expenditure as a risk factor for body-weight gain." New England Journal of Medicine 318.8 (1988): 467-472.
- Sahebjami, Hamid, and Raymond Scalettar. "Effects of fructose infusion on lactate and uric acid metabolism." The Lancet 297.7695 (1971): 366-369.