Summer is in full swing and 'tis the season of fad diets. But weight-loss experts say some pre-packaged diets sold at health stores go against almost all sensible advice.
Regardless, pricey products such as Celebrity Slim, OptiFast and the Lemon Detox Diet continue to fly off shelves.
Although these diets reduce a person's food intake to just a few branded syrups, shakes or soups, they are priced like a hearty meal.
Accidentally Overweight author Dr Libby Weaver said the stress of the diets could encourage the body to store more fat and, even if the number on the scale was dropping, it would more likely be dehydration, not fat loss.
Moreover, the diets hardly prepared people for the realities of eating regular food. "I'm a passionate advocate of eating food as nature intended it. You can't get much further from nature when you look at the ingredients in some of these products," she said.
Nutritionist Catherine Sissons added that a diet which required a change of lifestyle rarely brought permanent results. If someone regularly ate out and drank wine, their weight-loss plan should allow for it.
Of the three popular diets, Sissons rated the Lemon Detox Diet as the most dubious - the full version cuts out food for seven to 10 days. Instead, followers sip on a lemon juice and syrup mixture.
Sissons said this could cause a person's metabolism to grind to a halt in just 24 hours, leaving them weak and unable to complete basic activities.
"It would be like being in the bush with just barley sugar. You'd survive but your muscles would break down."
A safer and more effective detox would be consuming more fruit and vegetables and less red meat, coffee and alcohol.
The experts deemed Celebrity Slim and OptiFast little more than a "quick fix". The diets replace two meals a day with a branded shake, soup or meal bar.
In the medical fraternity, OptiFast is recommended to obese patients needing to lose weight very quickly before going into surgery, but anyone could buy it without a prescription.
Weaver said a successful weight-loss plan needed to address the issues underlying overeating. "Lasting weight loss is never achieved with a fad that starves your body and your soul," she said.
Lemon Detox Diet spokesman Andre Saade said the programme was not a weight-loss plan. "It's not a diet, it's a cleanse. Weight loss is just a side-effect."
He said there were several versions of the detox that included solid food. About 200,000 packs had been sold in New Zealand since it was launched seven years ago. Companies responsible for Celebrity Slim and OptiFast did not respond.
A seven-day Celebrity Slim diet pack (14 shake sachets, nine bars) retails for about $80.
A week's supply of OptiFast shake powder (enough for 21 'meals') is $65. The protein bars are about $4 each.
The seven-day Lemon Detox Diet is $87 online and includes syrup, herbal tea, salt, cayenne pepper and an information book. Lemons are not included.
Slim down without sacrifice
Radio personality Jacqui Jensen, 28, was a sucker for fad diets. She once lived off protein shakes for a month, and had to be hospitalised after another crash diet left her with severe vitamin deficiencies.
"I quite like a challenge, that's why I stayed on these things for so long. I was determined, even though I was miserable," she said.
"When I was on the shakes, my social life went. I didn't have a life. I stayed at home and did nothing; it made me depressed."
Last year Jensen decided enough was enough and called on the help of Nova Nutrition, a company which specialises in eating plans for people who don't want to sacrifice eating out and enjoying themselves.
"I went on holiday over New Year's and actually lost 3.5kg. There were treats, there were parties ... I had fun and I still lost weight."