This condition of low blood sugar and high insulin can be considered a step away from diabetes. According to the Zone theory, when you're creating this excess insulin, it also prevents your body from using its stored fat for energy. Hence, your insulin response to excess carbos causes you to gain weight, or you cannot lose weight. These people's systems overreact to an amount of carbos that others wouldn't have a problem with. This is why these people seem to gain or have trouble losing, while eating the same amount of food that doesn't cause others a problem.
Some people simply eat too many carbos.
They are metabolically fortunate. For the rest of us, we're susceptible to carbos. It's being documented that people are eating less and less fat, but getting fatter. Now, here's some theories to float. It seems likely that hypothyroidism, with its penchant for slowing down everything else in our systems, also slows down our body's ability to process carbohydrates.