By Duncan Kennedy
BBC News, Mexico City
To really appreciate Manuel Uribe's size, you have to do a bit of lateral thinking.
Picture in your mind an ordinary adult male.
And another. And another. And another. And another.
And, finally, one more. Seven fully grown men in all, standing in a line.
Now, add up their weight. Only then would you be getting close to Manuel Uribe.
The raw statistics are breathtaking.
At his peak, he weighed 560kg, or 1234lb, or 88st. That's half a ton. Small Japanese cars come in lighter.
I got a shock when I first met Manuel. He'd agreed to meet us at his home in Monterrey, northern Mexico.
I had expected him to be closeted in an upstairs bedroom, out of sight. But no.
No longer depressed
I stepped out of our taxi in front of what appeared to be a shop. And there he was - in the window.
The whole world can walk past gazing incredulously at Manuel as he lies on his reinforced bed.
It is not a shop, of course, it's his home.
More remarkably, Manuel has no problem with all the staring, not any more.
A short while ago, Manuel tried to take his own life, so depressed was he by his size.
But these days you could not meet a more engaging, funny and contented man.
And the cause of his new found happiness? His weight loss.
From being billed as the heaviest man on the planet, he is now heading for a different record.
The human who has lost the most weight. Here, too, the numbers are eye-popping: in the past year, Manuel has shed 180kg or 400lb or 25st.
Put another way, it is as if two fully grown men have climbed off his body.
"I am happy, I am really happy," he says.
No-one knows for sure why Manuel joined the ranks of the hyper-obese, or morbidly obese, as his doctors call it.
He lived for 14 years in Dallas, Texas, and he himself blames an unending diet of burgers, pizzas and fizzy drinks.
But the doctors and other scientists are not so sure.
They believe even the most gluttonous over-indulgence could not produce the kind of excess body weight Manuel has succumbed to. Instead, they think Manuel was super-sized by nature.
His nutritionist says the diet focuses on controlling his hormones
A fault in his genes which triggered the inflammation of his molecular structure.
Whatever the cause, the team of medics and nutritionists around him now have come up with a specialist diet that has produced remarkable results.
We arrived just as meal time was starting. One of five meals a day.
Manuel tucked into a delicious looking bowl of fish soup, complete with large chunks of fish. That was followed by a grapefruit and half an apple, rounded off with 18 peanuts. Yes, 18 peanuts.
Everything Manuel eats is calculated down to the last detail. Literally down to the last peanut.
"It's all about blocks," Manuel says. " My food is broken down into blocks. Every thing I eat has a value. A grapefruit is two blocks. Six peanuts are one block."
And so it goes on. By adding up the blocks he knows how much food he is allowed per meal.
All his food intake has been scientifically calculated to make sure he gets exactly what his body needs.
"It's about controlling his hormones," says Alejandra Garcia, one of Manuel's nutritionists.
"If he eats the right nutrients you control his hormones. If you control his hormones you determine his weight. It is not some outlandish fad diet. It is simple common sense refined by science."
That means they have worked out his exact intake of carbohydrates, proteins and fats. And, they say, this can be done for anyone.
As Manuel shuffles around the bed he has not left since 2002, he tells me he never gets hungry.
"I can eat chicken, kiwi fruit, even zero calorie cola drinks," he says.
'I chose life'
His mother Otilia agrees - she is the one who looks after all his needs, especially his food.
Manuel and his mother in slimmer times
"I am so proud of him now," she says. "He is so much more at ease with life."
His new food programme has re-energised his life - he now has a girlfriend and wants children.
He has bought a giant massage machine to maintain the circulation in the legs he can no longer close or move.
He has his own website and has started the Manuel Uribe Foundation to spread the word that weight loss for obese people is possible - and permanent.
His own body mass has been heading south for more than a year now.
Manuel says his aim to get down to 120kg, or 264lb or 19st. It means losing a further 260kg, or 572lb, or 40st.
That is like another three men climbing off his body.
"I take one day at a time," he says, "the doctors told me I had a choice. To choose life or to choose death. I chose life."
A smile then appears on the face of this larger-than-life character.
From Our Own Correspondent was broadcast on Saturday, 2 June, 2007 at 1130 BST on BBC Radio 4. Please check the programme schedules for World Service transmission times.