Please don't get too disheartened. 3 weeks is not very long at all and sometimes it takes a few weeks to get into the right pattern of exercise and eating to lose weight.

Rest assured that you are doing the right things by going to the gym and watching what you eat. I assume that you are filling your food diary in religiously, including snacks, and keeping to your calorie and fat targets? Sometimes it is easy to forget the things we eat and drink when we are out, but it is really important that you record everything as they all add up at the end of the day. Plus it's worth checking that you are being accurate about portion sizes. If you are selecting these from our database, then it is also worth weighing out what you are eating to ensure that what you call a 'medium' portion is the same as our definition. Portion sizes (creeping up!) are one of the most common reasons that weight loss can slow.

It helps to eat foods with a low glycaemic index (GI), as these are digested and absorbed slowly and keep you fuller for longer. They also tend to be more nutritious and contain many minerals and vitamins. I recommend that you base your diet on wholegrains i.e. wholemeal bread, brown rice and whole wheat pasta with lean protein, such as skinless chicken or fish, and lots of filling vegetables. Make sure your breakfast cereal is no-added sugar and, in fact, avoid all products that contain sugar. Low fat products can sometimes be quite high in sugar, so always check the label.

Finally, sometimes it can take a while to establish the right level of thyroid medication and this can affect weight loss. As you say your doctor has recently changed this, it may take a while before you feel the benefits. Meanwhile, carry on exercising and eating sensibly and all your hard work will eventually pay off. Good luck!