Why can some women eat whatever they want?

Hugh Wilson
Tuesday, January 4, 2011
AnnaLynne McCord. Image: Getty
McCord avoids the gym, eats like a pig, and stays infuriatingly slim and gorgeous. How unfair is that?
Hugh Wilson

Prepare yourself to dislike AnnaLynne McCord. In case you don't know, McCord is the 23-year-old star of TV show 90210, and one of the slimmest young women in Hollywood.

But how does she maintain her enviable figure? Does she live on lettuce water and rice cakes? Does she subscribe to some miserable fasting diet? Does she detox at every opportunity?

No she does not.

All in the genes?

According to a recent interview, her slender frame is down to nothing more than good luck and good genes.

"I am first and foremost very blessed with good genes," she told HollywoodLife.com last month. "As for diet, you're just going to hate me. You're going to be mad at me."

Yes we are.

"If I did not have good genes, I would be the size of a barn. I love to eat. I was at BBQ Blues or something on Santa Monica this morning — and oh my god, do they not have the best babyback ribs ever in the universe! The mac and cheese with four cheeses is ridiculous."

McCord avoids the gym, eats like a pig, and stays infuriatingly slim and gorgeous. How unfair is that?

But she's not the first Hollywood star to claim that genetics, rather than hard miles on the treadmill, is the key to a super slim physique.

"I don't really exercise and I eat all the burgers I want," Sienna Miller has claimed. To make matters worse, she described herself as "a real pig" who just can't put on weight. Lucky her.

Meanwhile, waif-like Keira Knightley says she loves eating pasta, cheese and chips, though presumably not at the same time. And angular Nicole Kidman has spoken about her love of pies and cakes while filming the movie Australia.

And it's not just the celebs

Nor is this phenomenon confined to celebrities. Katy, a 27-year-old copywriter, says she can eat pretty much what she wants, and never has any problem squeezing into a petite size 10.

"Seriously, I eat ridiculous amounts of Chinese food, pizzas, you name it, and I never put on more than a couple of kilos," she says, without even the merest hint of shame or apology.

So we may hate them, but they seem to be everywhere. Whether it's Sienna Miller banging on about burgers, Keira Knightley chirping about chips or the skinny office intern prattling about pies, there seems to be a bunch of women who can eat what they like and never put on a kilo. Like I say, they're easy to hate.

But are they easy to believe? Maybe you have to take some of this with a pinch of salt (or a huge knob of butter). After all, nobody likes to admit how hard they work to stay slim, especially in Hollywood.

Are some people naturally thin?

But skinny celebs may not all be telling porky pies, and may even be eating a few. Scientists have begun to suggest that some of us really are naturally thin.

And for those who are naturally thin, it may be really quite hard to get fat.

Some evidence for that has been around for years. In 1967 medical researcher Ethan Sims carried out an experiment on prisoners in the US. He asked them to gain an extra 25 percent of their body weight, in return for early release.

However hard they tried, some of the prisoners couldn't do it, even though they were consuming 10,000 calories a day.

That result was repeated in an experiment for a BBC Horizon documentary in 2009. Ten volunteers gorged themselves on pizza, ice cream, chocolate and chips for a month and did no exercise, and several found it very difficult to put on serious amounts of weight.

In other words, for some people it seems to be almost impossible to become obese. And many of those who do pile on weight find it quite easy to return to a normal weight when they stop gorging.

Nobody is quite sure why that is, but scientists are starting to think that we all have a set point for weight. We are biologically determined to be a certain size, and our bodies fight hard to keep us at, or near, that point.

The science bit

According to obesity researcher Dr Rudy Leibel of Columbia University, New York, "the body will constantly tend to try to bring you back to whatever your normal body weight is."

So if your set point is skinny, and you stuff yourself with pizza for a week, your metabolic rate will increase to try to compensate for the extra calories. But if your set point is heavier than you'd like and you try to lose a lot of weight, your body will fight hard to stop you doing it.

That's not to say that dieting is useless. Experts reckon that 50 percent of our weight is determined by genetic factors like these, and 50 percent by what we eat and what we do. "Genetics and development influence where this set point is tuned with regard to body fat," says Dr Leibel. "It is likely that environmental factors can do so as well."

But to counter the body's natural inclination to return to a set body weight, diets should be slow and steady.

"What's important about a set weight is that if you do want to change it, you have to be very slow," says Dr Carel Le Roux, an expert in metabolic medicine. In fact, Le Roux says the best way to gain weight is to go on a very low-calorie or crash diet. Your body will fight against it every step of the way.

So it seems that AnnaLynne McCord might be telling the truth after all.

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