Everyone has heard of the Low Carb phenomenon, but what we really should be thinking is Slow Carb, not Low Carb. Carbohydrates are an essential part of our diets - at least 55% of our energy should come from carbs. They are used as a fuel source in the muscles, liver and in the bloodstream and without a decent supply we suffer not only in physical performance, but also in mental performance.
If you restrict your carb intake you run the risk of running out of fuel. If there is not enough carb stored in your muscles you will run out while exercising, you may have heard of this being called "hitting the wall". This significantly impacts on your performance - if you have to stop your training session early you miss out on vital training adaptations and kilojoule burning. Those who limit their carb intake also run the risk of more grumpiness, lethargy and a decrease in mental function. The brain primarily uses carbs as its energy source - if this supply is limited the brain cannot function effectively - you end up feeling tired, irritable, unable to concentrate properly and with decreased reaction times. Not a nice side effect for you (or the people you interact with on a day to day basis!).
The reason that low carb diets are often associated with fast weight loss is that when you eat carbs you store them with water, if you dont eat enough the stores of carb and water are depleted (and this shows up as a loss on the scales) - you are not burning through body fat, therefore as soon as you start eating more carbs that weight will go back on as you store them + water.
What we need to do is switch from a low carb idea to a slow carb mentality. Slow carbs are those with a low glycaemic index. They digest and release sugars into the bloodstream slowly, and therefore dont have such a large insulin response. They keep us feeling fuller for longer as well (and are generally high in nutrients). Good slow carb foods are: wholegrain breads, lentils and pulses (e.g. chickpeas), kumara, basmati rice, oats, apples, yoghurt, bananas, kiwifruit and sweetcorn.