In Ayurveda, weight management is individual, and a lot of its depends on your dosha. Even Vatas, who are normally thin and lanky, may have problems with weight gain. For Vata types, weight gain may be because of a metabolism change, or because they are mentally stressed. Under stress, Vatas often eat irregularly, which disturbs the digestion. So for Vatas, routine is crucial. Vatas need to eat warm, cooked meals at a regular time each day, and make sure they get enough sleep. They need to eat in a relaxed, calming atmosphere and not be rushed.
Pittas have problems with weight gain when they don't eat regularly. They have a lot of fire in their system, and that fire needs something to cook. If it doesn't, then their metabolism slows down and toxins build up. It is important that Pitta types not skip breakfast. Hyperacidity is also an issue with Pittas, so they need to avoid both sour and spicy foods. Favor cooling foods and spices.
Kaphas are naturally prone to weight gain, and usually this stems from a slow metabolism. So Kaphas need to start with balancing the metabolism, increasing the ability to digest sugars and carbs, and getting on a Kapha diet and lifestyle routine. One way to boost metabolism is by adding some of the fire element into both food and lifestyle. Use spices that are pungent, such as pepper, ginger, and turmeric. Favor both bitter and astringent tastes, like leafy green veggies, beans, broccoli and sprouts. Make sure vegetables are cooked and warm, as raw vegetables are hard to digest. Quinoa and Basmati rice are both good grains for balancing Kapha because they have a drying quality to them. Sipping warm water throughout the day (allow water to boil, then cool before drinking) also helps to add fire to the body. Avoid heavy, cold, and fried foods. Exercise vigorously on a regular basis.
If you are overweight it could likely be a problem with your metabolism - this can affect you no matter which dosha type you are!