What seems to be more important is what you eat as opposed to how much you eat. Different foods affect your body in different ways. The human body is a highly complex biochemical system with elaborate processes regulating energy balance. Furthermore, different foods and macronutrients (fats, protein, carbohydrates) have significantly different effect on our hormones and the parts of our brain that control hunger and eating behaviour. Protein, for instance, stimulates the release of the satiety hormone, meaning that you will feel fuller for longer after eating. On the other hand, carbohydrates can lead to spikes in blood sugar levels, which can leave you feeling hungry again after they drop back down.
Finally, it is surprisingly difficult to burn large amounts of calories through exercise - and the calories burnt can easily be negated by your post workout meal.
The second reason exercising for weight loss doesn't work is psychological. Having been involved in competitive sports at a high level for most of my life, I understand what it takes to be in the best physical shape possible. When competing in national swimming, rugby and athletics competitions, my focus was always on specific performance goals, not aesthetics or weight loss; these are by-products of an effective and sustainable training program.
Obviously looking fit and healthy is great; it can help boost your confidence and overcome insecurities. However, lots of the common problems people encounter with exercise - such as imbalances, injuries, a lack of mobility and motivation - are often a result of making aesthetics their only goal. Putting how you look rather than how you feel at the core your training programme can be counter-productive, especially if injury breaks your routine and leads to extended periods of inactivity.
Your reasons for exercising should be positive rather than negative: train because you love yourself, not because you hate yourself. Celebrate what your body can do, don't punish it for what you ate yesterday.
If you want to make your training sustainable, you must be clear about what your focus or reason for training is; it has to be about more than just escaping a negative body image. When you start to train for positive reasons you will start to enjoy the process rather than enduring it for the sake of your waistline. Enjoying your training and exercise helps integrate it into your routine; it can become something you prioritise and make time for.
I often hear that weight loss is "80pc diet, 20pc exercise". There may be some element of truth in this, but the simple fact is if you want to transform your fitness, health and physique you need to give 100pc effort to both your diet and your exercise routine. There are few workable shortcuts in the fitness game.
