Low-fat diet 'burns more fat', study finds
HaggisWhisperer
Posts: 125 Member
Big headline on the BBC news website this morning - although I have to say the news article wasn't very informative:
http://www.bbc.co.uk/news/health-31763205
So I go off and try to find the source
https://endo.confex.com/endo/2015endo/webprogram/Paper20716.html
Which is an abstract of a poster presented at the Endocrine Society's conference this year - so not peer reviewed, although I expect that there will be a publication in the fullness of time. I dug into the abstract a bit, I don't really think what is in the abstract supports the low fat burns more fat versus low carb though. Well maybe it does, but only within the scope of the trial which I don't think is how most of us would define a low carb diet. The study was a crossover design (5 days maintainance calories then 6 days on a diet followed by a 2-4 week washout period then another 6 days on the alternative diet). Their definition of low carb was 30% carb, 49% fat and 21% protein - I normally eat around 1500 cal/day and for me that would equate to approx 113g carb, 75g protein and 83g fat (their low fat was 50% carb, 35% fat, 15% protein). I would usually consider a low carb diet to be at the very least <100g carbs so I was immediately a bit suspicious of the headline. I also don't think 6 days is a fair amount of time to rate a reduction in carbs - given the only moderate reduction in carbs I would hypothesise that there was still a fair amount of glycogen hanging about so the subjects would not have had a reasonable opportunity to effectively upregulate their fat burning). The authors do say that "Long-term extrapolation of our results is fraught with difficulties".
The authors haven't declared any conflicts that I can see.
http://www.bbc.co.uk/news/health-31763205
So I go off and try to find the source
https://endo.confex.com/endo/2015endo/webprogram/Paper20716.html
Which is an abstract of a poster presented at the Endocrine Society's conference this year - so not peer reviewed, although I expect that there will be a publication in the fullness of time. I dug into the abstract a bit, I don't really think what is in the abstract supports the low fat burns more fat versus low carb though. Well maybe it does, but only within the scope of the trial which I don't think is how most of us would define a low carb diet. The study was a crossover design (5 days maintainance calories then 6 days on a diet followed by a 2-4 week washout period then another 6 days on the alternative diet). Their definition of low carb was 30% carb, 49% fat and 21% protein - I normally eat around 1500 cal/day and for me that would equate to approx 113g carb, 75g protein and 83g fat (their low fat was 50% carb, 35% fat, 15% protein). I would usually consider a low carb diet to be at the very least <100g carbs so I was immediately a bit suspicious of the headline. I also don't think 6 days is a fair amount of time to rate a reduction in carbs - given the only moderate reduction in carbs I would hypothesise that there was still a fair amount of glycogen hanging about so the subjects would not have had a reasonable opportunity to effectively upregulate their fat burning). The authors do say that "Long-term extrapolation of our results is fraught with difficulties".
The authors haven't declared any conflicts that I can see.
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The data sounds, as you say, that they didn't give it much of a chance. Yet the BBC headline is what we want to see in the public eye. Let's hope they continue along this track.0
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Next week it will be "more fat in diet burns more fat" they change there minds so often.i originally thought low fat was best.but iv also lost fat eating a lot of healthy fat as recently iv read many articles saying low fat is bad for you.so confusing!0
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That was an odd study.
Carbs are only a problem if you eat excess calories. If you're eating at a deficit, of course all of the carbs will be burned rather than stored as fat. And, of course, if you eat fat, it will be burned as well (the fat oxidation they reference).
So in the 6-day diet, the LC group lost more weight, and the LF lost more fat.
What did the LC group burn for fuel when they were at a deficit? Apparently glycogen. So the extra weight loss was from water.
I guess that's interesting. But it has nothing to do with the "fat burning" claims of LC diets. It would have been more interesting if they had time to become glycogen depleted.0 -
I agree. I think most diets comparing macro composition should only start after the adaptation phase has passed. Granted, this means low-carb loses that early water-weight advantage, but I don't think it needed it in the first place.0
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Edit: Removed my incorrect comment.
The LC group still lost some fat. About 236g of the 1900g weight loss was fat. That suggests that most of the early weight loss in a LC diet is glycogen and water, but we sort of knew that.0 -
They didn't determine fat loss by body composition, they extrapolated it from a substrate balance which unfortunately wasn't in steady state.
800 cals taken out of intake, fat burn up 400 cals, 400 cals from glycogen reserves or errors or non-oxidative pathways or.....
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I kind of want to win one of those mega million lotteries just to set up my own research group. Put an end to all the not quite there studies and just do full on controlled, repeatable work that only reports measurable data. While they're at it, they can do the study exercise safety I've been waiting on from Penn State that I probably won't see for another 10 years.0
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