The most useful thing anyone can be told at the start is that body weight is regulated, not chosen. The body defends a weight it has held for a long time, and it defends it using mechanisms that do not consult you.
This topic is also in our free guide, Losing Weight Well. Get it emailed to you
Understanding that changes what follows, because most of what people believe about their own past attempts is wrong in a way that makes the next attempt harder.
The body defends a set point
Weight carried for years becomes the weight the body treats as correct. Reduce below it and several things happen at once: appetite signalling increases, satiety signalling falls, and energy expenditure drops by more than the loss of tissue alone accounts for.
These are not psychological effects. They are hormonal and metabolic, they are measurable, and they persist for a long time after the weight has come off — in some studies for years.
Why that matters for how you interpret your history
Most people who have lost weight and regained it conclude they lack discipline. What actually happened is that they succeeded at the hard part and then were subjected to a sustained physiological argument that most people eventually lose.
This is not an excuse and it does not make weight loss impossible. It reframes what the task is: not a period of effort followed by a return to normal, but a permanent change to a system that will keep pushing back.
What the modern environment adds
Energy-dense food available continuously, portion sizes that have grown, sleep that is shorter than it was, stress that is chronic rather than episodic, and a level of daily movement that has fallen substantially in two generations.
None of these individually explains much. Together they explain a great deal, and they explain why the problem is population-wide rather than individual.
Where medical treatment fits
For a long time the available options worked against the defended set point and mostly lost. Current medical and surgical treatments work differently — they intervene in the signalling itself rather than asking people to override it.
That is why results with them differ in scale from results with diet alone, and it is not a moral distinction. More on medication and bariatric surgery.
What this site is for
Most information about weight stops at the point the weight comes off. This site is mostly about what happens after that, because that stage is barely written about and is where people arrive with questions nobody prepared them for.
If you are at that stage: what happens next.