I have had the dreaded runner's trots a few times. Dreadful feeling. Especially when you're caught miles from home and in a deserted area with not a toilet in sight (happened to me but I will keep the full story to myself).
Go to this site for a basic understanding. I encourage everyone to give it a try. http://www.montignac-intl.com/eng/met_en.htm
I had absolutely no idea about nutrition and had yo-yo dieted from puberty until I was 24 until I read Michel Montignac's book 'Dine out and lose weight', which covers all the principals of the method in detail. I found that I was lethargic and disinterested in life before I discovered this healthy way to eat and live.
His book for women is superb as it takes women through all the stages of their lives.
To lose weight, I followed the first phase of the method strictly and the weight dropped came off easily. I also felt a lot better in myself. It was wonderful! It's a life plan so it means you never have to worry about going on a diet again. It's so easy.
I don't follow it rigidly now, but I follow the basic guidelines along with my own rule of 'everything in moderation'.