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Are protein shakes the weight-loss magic bullet?

Anyone who is looking to lose weight and has seen Rick Rubin lately is probably heading straight for their blender.

Mr. Rubin, the famed record producer and co-president of Columbia Records, recently lost 130 pounds (almost 60 kilograms) thanks to a six-days-a-week workout regimen and a strict diet of fish and protein shakes. He can be seen showing off his new buff bod in the latest issue of GQ, in which he is interviewed alongside Kid Rock.

Protein shakes, it seems, have become a constant for Mr. Rubin who has worked with the Beastie Boys, Johnny Cash and Shakira. "He was in the studio cutting up apples and drinking his shakes," Kid Rock told the magazine.

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So is the Rubin diet the secret to weight-loss success? Protein shakes, typically made from powdered supplements, have become a staple in the fitness community, where they are seen as a needed way to build and repair muscle tissue. They help push annual sales of sports nutrition products, which now top $2.7-billion (U.S.) in the United States, according to Consumer Reports and their benefits are frequently touted by bodybuilders such as last year's Mr. Olympia winner Jay Cutler. Actress Hilary Swank reportedly relied on drinking protein shakes for breakfast and throughout the day to get buff for the boxing movie Million Dollar Baby.

But many trainers are skeptical of their benefits for the average person trying to get fit. In some cases, they could be damaging. Drinking too many of them could lead to weight gain and can pose a range of health problems, including dehydration, increased risk of osteoporosis and kidney problems. Trainers say it's better for most people to opt for a well-balanced diet instead.

"Most people already eat more protein than they need," says Shayla Roberts, owner of Evolution Coaching in Vancouver. Protein shakes may be a good "quick fix" for people looking to lose weight, since protein makes us feel full, but drinking them is not a good long-term strategy when it comes to dieting, she says.

"You will eventually have to return to eating food, and if you haven't changed your eating behaviours then you are not going to maintain your weight loss," Ms. Roberts says.

Considering that the shakes can contain up to 40 grams of protein a serving, consuming too many of them can be harmful and may even lead to weight gain.

"The fact of the matter is the body can only break down about five to nine grams of protein per hour. So any excess protein you are not using for athletic endeavours or energy can either be turned into fat of excreted. So if you are consuming more protein than you need and you are not athletic, you are either going to get diarrhea or you will probably store that protein as fuel, which is fat," says Shannon Jones, a trainer at Crossfit Zone in Victoria.

Excreting that extra protein can put pressure on the kidneys and lead to bone loss, as calcium is taken from bones to assist the excretion process.

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While she drinks one protein shake for breakfast, Ms. Jones says you should avoid drinking them unless you lead a very active life.

"It's not going to benefit you in any way," she says.

Some people who lead very active lives, however, consider their protein shakes essential.

"You just cannot physically consume that much protein in a day in a solid form," says Coco Kissack, a fitness competitor in Winnipeg who drinks between four and seven protein shakes a day.

But the 39-year-old stresses that those shakes are consumed on top of a balanced diet.

Still, that doesn't stop people looking for a magic fix from frequently asking her if protein shakes will help them get buff bods like hers.

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"I get approached by a lot of people who see me working out who ask about their diet, and they think they can just take these products and it's going to help them out," she says.

Unless you're working out as strenuously as she does, they won't.

Some, in fact, may be toxic.

An investigation released this summer by Consumer Reports found that all 15 of the protein drinks it tested had at least one sample of arsenic, cadmium, lead and mercury. While the levels of contaminants found in most of the drinks were in the low to moderate range, the investigation also found that for three of the products, anyone drinking three daily servings of them could be exposed to levels of arsenic, cadmium or lead that exceed the maximum limits for one or two of those contaminants in dietary supplements proposed by the U.S. Pharmacopeia, an organization that sets voluntary standards for health products.

While some people may be lured by the promise of losing weight and getting ripped, the Consumer Reports study should give pause to anyone thinking they can achieve those goals with a heavy diet of protein shakes, Ms. Jones says. The shakes should only be used to supplement a well-balanced diet, not replace it, she says.

And considering the chemicals you could be ingesting when you're chugging down a protein shake, it may be best to just opt for real food instead, she adds.

"If you want to have a nutritional diet, you probably should weed out the overprocessed substitutes and try to eat food instead of powder."

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