"Once I've lost it, I'll keep it off"

The fresh start assumes that the hard part is losing, and that keeping it off is a matter of not being silly afterwards. Eat sensibly, stay careful, and the new weight holds.

Priya Sumithran and colleagues, in 2011, put fifty overweight or obese people on a ten-week very low energy diet, and they lost about thirteen and a half kilograms each, which is over two stone. Then the researchers measured a panel of hormones that regulate appetite, and asked people how hungry they were, at the start, at ten weeks, and a year later. At ten weeks the hormones had shifted in the direction you'd expect. The ones that signal fullness had fallen, the one that signals hunger had risen, and people reported feeling hungrier. The question was whether that would settle. At sixty-two weeks, most of the hormones were still shifted from where they'd started, and so was hunger. A year after losing the weight, the body was still, measurably, asking for it back.

The most extreme version of this comes from a television programme. Erin Fothergill and colleagues followed fourteen contestants from an American weight-loss show for six years after they'd lost, on average, fifty-eight kilograms. Six years on they'd regained about forty-one of it. But their resting metabolic rate, the energy the body burns doing nothing, was about seven hundred calories a day below where it had started, and about five hundred below what you'd predict from their body size. Their bodies were running slower than they should have been for their weight, years later, and the contestants who'd kept off the most weight showed the most slowing. That's an extreme case, from an extreme intervention, and I wouldn't extend the numbers to an ordinary diet. But the direction is the same as Sumithran's, and it answers the belief in this chapter. The body isn't neutral about lost weight. It defends it, with hunger and with a slower burn, and it goes on defending it long after the diet has ended.

None of this means weight can't be lost and kept. Some people do it, and Anderson's average shows a little is kept by most. What it means is that the regain isn't you being silly afterwards. It's a body doing what bodies do after a diet, and a person who's been through that a dozen times and blamed themselves a dozen times has been blaming themselves for having a body.