Consumption of Added Sugar Doubles Fat Production

Just came across this interesting study, and thought I would share it, as a lot of us are probably “fuelling” with sugary drinks on our bikes.
Perhaps we should consider using an energy source biased more towards glucose.

UZH - Consumption of Added Sugar Doubles Fat Production


Looks like that study is for general consumption of sugar for “normal” people. Very different when working out. We’re burning that sugar faster than we can eat it so how could it possibly develop into fat?


TLDR: that doesn’t happen during training at all.

Longer version:

The ability of the human body to burn through glycogen during exercise, and immediately lower blood glucose as a result is amazing! During training sessions like that, GLUT4 (rhymes with “scoot”) is upregulated/activated. GLUT4 is a transport protein that exists mostly dormant in muscles until exercise happens, or you eat a donut (or other sugar). GLUT4’s sole job is to act as a vacuum for muscle cells to suck glucose out of the bloodstream and into the working muscle. Exercise is the number 1 way to activate GLUT4 and make all those vacuums present on the muscle cell membrane turn “on” and do their job (rather than sitting idle and dormant deep inside each cell). They remain highly active for at least 30 minutes post-exercise. It also exists in the liver, which is how you get carbs converted to fat (bad for body composition!) but interestingly, and importantly, the GLUT4 in the liver stays relatively dormant during exercise while the muscle cells get to vacuum up all the sugar in the blood.

The application of this GLUT4 activation is that any sugar you consume will be sucked up by the muscles and prevented from circulating your bloodstream and causing inflammation, or causing insulin to spike and remain high until the liver turned it into fat. There will be NO fat generation or chronic low-grade inflammation caused by that rapid sugar influx, so long as it’s either during exercise or immediately post-exercise.

Now, if you were to consume sugar in higher doses around the clock… then you’d have problems. Ironically, consumption of sugar during and immediately post-exercise may actually improve body composition because the storage of muscle glycogen in muscles (glycogen = storage form of carbs) is a fat-burning process AND muscles that are stocked with glycogen tend to build more muscle proteins at rest which is also fat-burning and blood-sugar-reducing.


Fantastic answer! Do you know at what intensity the glut4 transporters are activated at? Is walking enough? Or does it have to be something higher?


Walking is enough. At least for the type 1 muscle fibers. Unsure on 2’s.

I’m not sure on how low the activity can be to have a meaningful increase in glucose uptake, but it’s low enough that anything anyone on this forum would consider even light exercise would do it.


Thanks, that was a really enlightening reply.
I am no longer worried about chewing through mountains of sugar while riding :slight_smile:

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Me neither! Phew! My wife has consumed >1,700g of almost pure sucrose on a couple ultra-distance rides now. Healthy a1c & fasting blood glucose. 5’9" 140, 15% BF (very lean), with no change in trend over the last 3-4 years. I consume lots too but her numbers are a more impressive anecdote


My view tends to be , be good about your diet during the vast majority of your time. Don’t worry about it during exercise or events.


This is why I take up to 100 grams of carbs in an hour recovery ride…no better time to carb load/restock glycogen

Could this be done on Keto? While exercising, the sugar just keeps circulating in the blood until it’s burned. Once you stop exercising, you stop the sugar and it won’t affect the diet?

Yes. If you do that, expect possible hypoglycemia post-exercise.