hi... removal of spleen does not cause weight gain...you need to check your food habits and activity levels..make sure you exercise like brisk walk/swim/ dance for 1 hour daily.. eat small meals every 2-3 hours.. fruits, nuts for breakfast, sprouts salad as mid meal, salad with lunch..avoid wheat and have brown rice/ quinoa/ oats.. egg whites as evening snacks .. keep dinner light like soups, salad, grilled non veg.. avoid fried and sweets as much as possible.. rest well..drink lot of water..