Bread / Pasta/ [insert carb here] makes you fat. Or does it? Carbohydrates have had a tough decade. Pretty much since Gary Taubes’ 2010 book ‘Why We Get Fat’ they have been demonised based on the hypothesis that carbs spike or elevate insulin and insulin as the ‘fat storage hormone’ makes us store calories as fat.
It’s a nice hypothesis, with just the right amount of science to sound scientific enough for popular press and the million headlines and low carb diets it spawned. Sadly it’s incorrect.
There are now two metabolic ward studies that debunk this. If you’re not aware, a metabolic ward is basically a room you’re locked in for a few days and nights where absolutely everything that goes in and out of you is measured. This includes your energy expenditure and most likely your body composition by a DEXA scan .
It’s the gold standard in nutrition research and very expensive, consequently there are not many studies using them. So when they do come along we should take notice.
What Do The Studies Say?
The first, a first metabolic ward study, controlled diet and exercise to precisely compare the effects of a low-carb diet with those of a low-fat diet. It’s important to note here that protein was kept constant across both diets, i.e. carbs were replaced purely with fat in the low-carb diet and vice versa. Both diets led to an equal amount of fat loss so it was total calories that mattered not whether they were from carbohydrate or fat.
In 2016, the same researchers repeated the study with an even lower level of carbs, down at ketogenic levels (some people complained the first study was not low carb enough). Again though, the low-carb diet showed no improvement in fat loss over a low-fat diet.
Low-Carb vs Low-Fat
The results from these metabolic ward studies are clear but there is some evidence, anecdotal and otherwise, that in real life low-carb diets can lead to greater fat loss than low-fat diets. How, given the results of the studies above? Not because of a reduction of carbs and insulin but rather because restricting carbs can reduce calories by narrowing food options (no cake…) and almost by definition increasing protein intake.
Certainly refined carbohydrate and sugar are no good for you in quantity, but that doesn’t mean you need to throw them all out of your diet.
It is calories, not carbs, that really matter in terms of fat loss, whichever dietary strategy helps you achieve this is the right one for you whether that’s low carb, high carb or somewhere in between.
Finally a word of warning. If this has inspired you to do some of your own research, the low carb vs low fat debate is one of the fiercest fought online. You’ll see an amazing amount of spin and name calling on both sides. Read from reputable sources on both sides and take care.