The answer: ‘Most of the current high protein diets are low in carbohydrate, forcing the body to use it’s muscle glycogen stores and also to break down protein to form glucose (we can’t convert fat to glucose). Each of the 600 or so grams of glycogen is stored in the body with 3grams of water so the loss of glycogen results in water weigh loss. More water is lost as the body excretes the left over parts of the protein. The WW programme is designed for long term fat loss. When people loss weight fast, most of it is back in 6 months with a few bonus kilos.”
We see uninformed and ignorant comments like this all the time. Snippets of information that, taken in isolation, makes the low-carb diet look bad.
What this person is trying to say are two things; (1) that all the weight you lose is water; and (2) the body has to break down muscle to glucose to continue to function.
Lets just analyse this for a second. It is true that by not eating carbs you use up all your glycogen. When you lose glycogen you lose a lot of water. But what she fails to mention is that you normally use up all your glycogen within the first 48 hours. Weight losses after 48 hours can not be explained by loss of water! And of course, we as educated people know that weight loss after 48 hours is mainly made up from losing fat
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Her second hypothesis is even more ignorant. Yes, it is true that the body cannot convert fat into glucose (well, almost true, the body can actually produce around 15 grams of glucose a day from fat, but that's another story!), but that is quite irrelevant. The body can convert fat into ketones which mimicks glucose. We all know that the body and brain is more than happy using ketones instead of glucose!
It is also true that the body can convert protein (or Branched Chain Amino Acids, BCAA) to glucose, but only under certain circumstances. If you eat enough fat and quality protein (this is why a quality protein supplement is important) you will not cannibalise your muscles. As a matter of fact, in my experience with 100's of people, muscle loss is much more prominent in the low-fat diet.