They are never a good idea. They always have nasty side effects. Some are addictive. The less weight you have to lose, the harder it is, but it is a simple equation; you need to burn more calories than you consume. Try keeping a food diary of everything you eat per day. You may well find that you actually eat more than you realise- snacks etc. You may also find that you are eating big portions, or food which is higher in fat than necessary. Just by swapping to lower fat versions you can save yourself calories. Have one piece of toast in the morning rather than two. Take the stairs rather than the lift. Don't eat after 7pm. Try a new sport like swimming which you will enjoy, rather than forcing yourself to do Davina every now and again! Cut back on alcohol if you drink- only drink 1 day a week rather than 2 etc. Also, it is OKAY to be a bit hungry! The way I rationalise it is, if I am a bit hungry, then I am using my fat stores for energy rather than eating more. I need to use my fat stores as I have too much fat! So, being hungry is just your body saying "Feed me! You usually feed me now!!" when actually, feeding is not always necessary.
Also eat and chew slowly, and really listen to your body- stop when you are "content", not full or stuffed.x