There are many reasons why you may gain weight and the cause may not be one factor but a combination of a number of different ones.
Well more precise yo-yo crash dieting! Dieting makes you fat. As you reduce your food intake to lose weight, your body put itself on 'famine alert'. Your body knows its not receiving enough food to function properly and therefore it slows down your metabolism to get the best use of the small amount of food it is receiving. When you say you want to lose weight, what you actually want to lose is fat. If you lose weight rapidly, almost 25 percent of that weight loss can be made up of water, muscle and other lean tissue. Losing more than 2lbs per week of pure fat it near impossible. So when you lose 5.6 somtime 10lbs in a week on a crash diet you must remember much of that weight is from water, muscle and tissue. When you crash diet you lower your metabolism and store MORE fat despite losing lbs on the scales! While training with ourselves you will may lose weight in great volumes in the first few weeks but we will make sure its not due to fad diets and unrealistic health plans and more importantly that you can maintain this new weight.
Too much food and not enough exercise
This is the obvious reason, because if you eat more than you burn off then you are going to gain weight.
The Type of Food You Eat
Every time you eat, your body has a choice: it can either burn that food as energy or store it as fat. Researchers have found that high insulin levels cause you not only to change your food into fat, but they also prevent your body from breaking down previously stored fat. These fast-releasing foods include anything that contains sugar and refined flour, such as cakes, biscuits, pastries, and other 'treats' and all the bad WHITE foods- white pasta, bread, rice and so on.
There are two types of allergic reactions.
Type A (classic allergy). In this type of allergy, you will experience a reaction immediately after contact with an allergen (such as shellfish or peanuts, for example).
Type B (delayed allergy or intolerance). Here the reaction can take place between one hour or three days after ingesting the food. Symptoms such as weight gain, bloating, water retention, fatigue, aching joints and headaches can all be due to a Type B allergy.
Other reasons could be: