Cut fat or cut carbs? New research says fat


So when it comes to the best way to diet to lose fat. there’s a never-ending debate on what works better: cutting fat calories, or cutting carb calories. There are debates about which is metabolically more effective, there are debates about which is easier to adhere to in terms of eating a satiety, and personal results vary.

Personal results vary especially because (and no offense, anyone) we all suck at guessing how much we’re eating. Unless you really carefully measure everything, you’r probably not consuming the amount you think.

There’s a new study that did the most careful kind of test - the subjects came lived in a metabolic ward to exactly measure fat burned while they were give exactly measured amounts to eat. No guessing; every calories was counted.

They found that, calorie-for-calorie, reducing fat was much more effective than reducing carbs. Caveat: these subjects were all young obese individuals; the results may not be similar for other age groups or non-obese individuals.


Subjects were first put on a 50/35/15 maintenance diet for five days to stabilize.

Then their maintenance calories were reduced by 30% for six days - either by cutting back the fat, or by cutting back he carbs. Importantly, the amount of protein stayed the same. (It’s easy to accidentally cut your protein if you go low-fat, and that can lead to loss of lean tissue instead of fat.)

It the metabolic lab, they were measuring exactly how much fat each person burned. Fat burned minus fat consumed is presumed to be the amount of body fat lost. Result: the low-fat diet led to 67% greater loss of body fat.

Important note: this is not a knock on the new, higher-fat formulation of Soylent 1.4. The formula is not intended as a weight-loss diet, it’s intended as a healthy 100% maintenance food. Moreover, the higher fat proportion was intentionally done to improve satiety on this liquid diet - if you’re not satiated, you’re tempted to eat more, even if you’ve had enough calories.

But this should give pause to those who are convinced that cutting carbs is the one and only true way to lose weight. Both groups lost fat in this experiment, because both groups cut calories - and what diet will work best for you depends a lot on how well you can stick to it.


Did both groups lose roughly the same amount of weight overall?



The results will be presented in a poster Thursday, March 5, at ENDO 2015, the annual meeting of the Endocrine Society, in San Diego.

So other than the press blurb in the article @MentalNomad provided I can’t find much additional information about the study, but there is this:

Compared to the reduced carbohydrate diet, the reduced fat diet led to a roughly 67% greater body fat loss.

So I don’t know how much people lost, but people on the low fat diet lost two thirds again as much weight as those on the low carb diet.


No they lost 2/3 more fat not necessarily 2/3 more weight. They could of lost muscle mass as well and lost the same amount of weight overall.


As @gambit points out, this is not currently a published study, so we can’t easily dive into the detail - it was presented in conference just yesterday.

And @horsfileld is right, they could have lost more lean tissue, as well as losing more fat - but I don’t think it’s likely; carbohydrate is known to be more muscle sparing than fat, though less muscle sparing than protein. In fact, without knowing more detail, we don’t even know if they measured weights. But the detail on the fat-burning impact of diet composition is interesting in and of itself.

I hope the study provides detail about overall metabolic rate - how much of the difference in fat burned is attributable to the TEF? (Thermic Effect of Food - the idea that carbs stimulate the metabolism more, and therefore cause more calories to be burned.)

Also, I’d like to see the study itself to make sure it was isocaloric on protein. That’s implied by the description, but I want to make sure. Variance in the amount of protein between groups is a huge confounding variable for far, far too many carb vs. fat studies. The group with lower protein almost invariably loses a higher proportion of lean tissue, and therefore a lower proportion of fat.

I have a lot of unanswered questions… but if low-carb was really “The” way to lose fat, we should have gotten a very clearly opposite finding, here. Looking forward to being able to ready the study & response to it.


The ENDO 2015 conference runs through March 8th - there may be more detail in the post-conference write-ups, but more importantly, I should think presentation and feedback in conference speeds the road to publication… so I’m hoping within a few months.

“The Annual Meeting Steering Committee invites all endocrine investigators to submit Clinical Trials abstracts to ENDO 2015. Clinical trials accepted for presentation at ENDO 2015 may be submitted to The Journal of Clinical Endocrinology & Metabolism through the Clinical Trials Express program.”