I completely agree, one of the most important keys to weight loss is controlling portion size. Many people focus far more on 'what' to eat when their issue is more with 'how much'. Benefits aren't limited to those wishing to lose weight, there are many people suffering faigue, emotional imbalances, bloating and various other symptoms primarily because their portion sizes are too large.
It is a case of each to their own unfortunately, extreme carbohydrate cutting is a very controversial diet in itself besides the fact that everyone's body is different. Some people feel great on a lower arb intake, others not so good.
Cutting carbs to <20g is essentially a ketogenic diet. The ketogenic diet is known primarily for it's use with epileptic children, it's been successful in helping with certain types of seizures in just over 50% of cases. Unfortunately in adults the diet wasn't shown to be very successful.
The diet has become very popular among dieters and weight lifters who take advantage of the ketogenic state for fat burning.
There are very good arguments both for and against ketosis. It's generally agreed that after the initial feelings of being hit by 50 trucks, you become more energetic as your body adapts to breaking down fat for energy. As your body breaks down fat, ketones start to build up in your blood. For most people this doesn't appear to cause any immediate issue and can be detected using the bran Ketostix or similar product. Excessive build up of ketones is thought to cause the blood to turn acidic so this state should be monitored with care. As good as ketosis is reported as being for fat loss, harmful long term effects on the body are still up for debate. Current known effects include kidney stones, liver disfunction, and high cholesterol.
Personally, from my own research and experience (yes I have followed this diet myself), I believe a ketogenic diet to be acceptable in the short term (two weeks). Long term use of this diet should be avoided as it's potentially very harmful to the body. Our bodies are not designed to live in a state of ketosis for any prolonged period of time.
However, lowering your carbohydrate consumption, especially if you have been consuming a high amount of carbohydrate for some time, could benefit you in the long run. By lowering your carb intake I mean no lower than 120g, this will allow you adequate fuel to function healthily while helping avoid the negative effects of consuming too much carbohydrate. This is my recommendation and is not official.
DPGfitness, you're not a weight lifter by any chance are you?