So you'd like to gain some weight. First thing to do before looking at your diet is to speak with your GP and have your thyroid tested to make sure that there is no underlying medical reason for being underweight.

Rule number one, being underweight does not give you carte blanche to devour the desert trolley, to gain weight healthily it is imperative that you make healthy choices.

The next point is to NEVER skip a meal, you must eat three meals a day and two to three healthy snacks as well.

The key is to increase your calorie intake while still being healthy, eat extra healthy calories. Some people naturally burn up more energy so you need to make sure you eat adequate carbohydrates and fat so that your body doesn't look to burn up the protein in your body for it's energy.

• Carbohydrates should be as unprocessed as possible, whole grains will give your body more energy.
• Fats should come from unsaturated sources such as nuts (although not peanuts) & seeds.
• Protein is also essential for weight gain and this should come from lean sources such as lean meats, fish, seafood, beans (Soy Protein) & legumes.

So, when you're planning your meals include a complex carbohydrate like brown rice as this will convert into glucose slowly and allow your body constant energy. Also include healthy protein as this is what will increase your lean muscle mass (you don't want to gain weight if it's going to make you wobble!). Then you need to add fat so that your body has a secondary fuel source.

Simply adding a couple of Herbalife shakes a day to your daily diet will give you the recommended extra 400-500 calories a day you are looking for to gain weight healthily and steadily over time.