This is because your body tries to “defend” its fat stores to maintain your highest weight (this is what researchers call “starvation response”). This is why when you go on a diet or begin exercising, weight loss becomes progressively more difficult and the weight will come back as soon as you stop or reduce your efforts at keeping it off.
While short-term “quick-fix” solutions can sound appealing, they are usually temporary and are therefore linked to high rates of weight regain. Weight management is never about how much weight you can lose or how fast you can lose it – all that matters for your overall health and well-being is how much weight you can keep off while still living a life that you can enjoy. This is called your “best weight”.