Willpower gets far too much of the blame. The reasons weight builds up, and then refuses to come off, are largely biological. Understanding them is the first step to treating them properly.
Appetite and fullness are governed by hormones, not habit alone, and in many people those signals are turned up loud. That is why sensible eating on its own can feel like a losing battle. That is also why doctor-prescribed weight loss injections help so many people finally get traction. These work with those appetite signals. Metabolism plays its part too. It slows with age and drops further when muscle is lost through crash dieting. So, each failed attempt can leave the body a little more efficient at holding weight.
Then there is life: desk-bound days, broken sleep, stress and the odd medication all nudge the balance the wrong way. Some fat is simply genetic, laid down in pockets around the stomach, flanks or chin. These stay put at any size. The NHS guidance on obesity is a clear, non-judgemental summary of the health side. It underpins the honest conversations we have here. None of this is a character flaw. It is physiology, and physiology is something a medical team can actually work with.