Trying to shed a few pounds? Maybe all you have to do is climb into bed with a special someone ... and stay awake.

According to an upcoming book — and celebrities like Angelina Jolie and George Clooney's former model-girlfriend Lisa Snowdon — the key to controlling weight is simple: Have more sex!

"A steamy sex life could be the best diet you've ever tried," said author Kerry McCloskey, whose book, "The Ultimate Sex Diet: The Secret Formula for a Slimmer, Healthier, More Passionate Life," will be in bookstores early next year.

In "The Ultimate Sex Diet," various positions and "sex-ercises" are described in detail, including "crunchy kisses," "Elvis' pelvis," "wheelbarrow of fun" and other erotic moves to help you get fit while doing some ultra-intimate bonding with your partner.

But a strenuous sex life doesn't only help you lose weight. Other health benefits include a longer life span, reduced depression, an improved immune system and a stronger heart.

Spending quality time in the sack can also make you look better — a 1999 study by Dr. David Weeks at Scotland's Royal Edinburgh Hospital found that an active sex life can make you look up to seven years younger.

While experts agree that sex is good for you, they're not convinced about McCloskey's weight-loss claim.

"The caloric expenditure for sex is high, but the time frame is short. People generally don’t maintain that level of expenditure for very long," said Dr. Mary Vernon, President of the American Society of Bariatric (Weight-loss) Physicians.

However, "normal sexual function is part of normal human functioning. There are benefits from sex in terms of relaxation, pair bonding, etc. In terms of weight loss, obviously if someone is supporting you, you can do much better work," she added.

Dr. Robert Friar of Ferris State University in Michigan argues that while sex does have health benefits, it's not going to directly affect your weight.

"If you lose weight through sex, it's because having a partner that makes you feel good increases your self-worth, which makes you less likely to be depressed. Even mildly depressed people eat more because the serotonin that signals when you've eaten enough is low," said Friar, a physiologist who has done extensive research on the benefits of sex.

"Most books that are written about sex for the popular press are written to make money. They are not designed to help people," he added.

Perhaps with these critiques in mind, McCloskey, who cites various studies in her book, advocates extending lovemaking sessions to make them more beneficial, as well as increasing their intensity and frequency. The goal is to have a lot more sex than the average couple, she says.

She also mentions that moderate exercise outside of the bedroom is important (more exercise leads to better sex, and vice versa) and includes dietary guidelines.

And at least for one couple, the diet is working.

"My fiancé and I started trying out some of the ideas, and it was so much fun! More than anything, I think it helped us get closer as a couple," said Jennifer, a marketing executive in Dallas who asked that her last name be withheld.

"We started cooking together to help improve our diets, and I ended up losing 23 pounds over the six months since we've been doing it. Eventually it just became a lifestyle, and now we don't even think about it."

McCloskey also has creative ideas for using food in … different ways. A la "9 1/2 Weeks," she suggests feeding each other as a method of revving each other's engines, as well as incorporating various vegetables into your diet, including many "that are phallic-shaped and extremely nutritious."

Celery gains a key mention in the book, where McCloskey cites sources who say the veggie is packed with pheromones that attract women, making it the perfect low-cal snack for the male partner.

And for those who crave sweets, there are certain fruits that can serve as aphrodisiacs, including grapes and oranges. Bananas are even said to contain ingredients that boost male erective efficiency.

McCloskey also touts the positive effects that good sex can have on a relationship.

"The top two reasons why relationships fall apart are that people stop communicating and stop having sex. This is a fun way to have more pleasure in your life, and improve communication in your relationship," she said of her diet.

But what about those not lucky enough to have that special someone?

"I think there are still elements of the plan that you can apply to your life, like using your sex appeal as motivation to lose weight," said McCloskey.

But doing it by yourself might not be as much fun.

"Life is short, so enjoy the ride," McCloskey says in her book, "especially the free one that your partner gives you!"