Wednesday, March 30, 2011

Do Low Carb Diets Work?

As I mentioned previously, my topic of study at med school last week was diet and obesity. I thought I would quickly post up the results of a study carried out on the efficacy of different diets, as its quite interesting to anyone on a low carb diet.

Basically, in the graph below we see the results from two diets, both limited to 800 calories a day, and both lasting for 10 days. One was a 'balanced' diet, with a mix of carbs, proteins and fats, and the other was very low carb. Here are the results after 10 days (click to enlarge):

 To break it down quickly, if you look at the GREEN column, you can see that the low carb diet caused nearly twice the weight loss of the mixed diet. This is why they are so popular - you see good results fast. But if you look at the YELLOW column, you'll see that both diets led to exactly the same loss of fat. So where did the extra weight loss come from on the low carb diet?

A glance at the BLUE column will show you that nearly all the extra weight lost was just water, which can very quickly go back on when you start eating a balanced diet again. This means that people who start low carb diets often see their losses go right back on when they reintroduce carbs. Perhaps more worryingly, the RED column shows that more protein was lost in the low carb diet - and that is pretty much all coming from your muscles.
So there you have it - you DO lose fat on the low carb diet, but not any more than you would on a regular diet. You do, however, see weight drop off quickly, albeit with a lot of water and some muscle loss.

For myself, I've still restricted the amount of carbs I eat, as they are what I would always binge on in the past, and protein does make me feel fuller for longer. But I'm careful to get some fruit and veg in there, or to occasionally make a sandwich or something else with some carbs in, just to try and preserve as much muscle as I can (and prevent skewed results from water loss). I see building muscle as the second stage of the Idle To Idol project, after the loss of body fat, and don't want to burn up too much of what I already have!



  1. I've never had to do any diet, I never gain a lot of fat even if I go a period of time without exercise. This would be helpful one day though I'm sure. :) Good to know.

  2. From experience the only thing that really works is a lifestyle change, not fad diets.