Increased body weight may not be just due to lifestyle options but can signify underlying medical disorders like thyroid insufficiency, hormonal issues etc. Fatigue is often as associated symptom in such people. Please visit a doctor for proper checkup, diagnosis and treatment. In such cases, weight loss may require a holistic approach combining a nutritious diet, appropriate exercise regimen and medications as required. This can show you changes within a few weeks and motivate you to continue with the regimen to achieve your desired weight and give you a boost of energy by improving your overall health.