New fad diets might show positive results on the weighing scales but could result in long-term damage to your health. Photo: IC

As summer approaches and layers of clothing are shed, the need to get in shape leads more people to experiment with this season's fad diets. Among the long list of potential body-sculpturing meal plans is the raw fruit and vegetable juice diet.

Renowned as it may be for accelerating weight loss, nutritional experts warn that like most fad diets it is not an effective way to lose or keep weight off, and may even cause dieters health problems.  

Yang Xu, 30, has been on the juice diet for the past six months in an attempt to lose weight. By substituting his lunch everyday for juice and cereal, Yang sacrifices only one meal a day and eats a normal breakfast and dinner. Despite Yang's efforts, his weight has remained the same 80 to 85 kilograms that it was when he started.

"The diet is not working for me," said Yang, who started the diet after a bad leg break last October. He began the juice diet to lose body weight and reduce excess strain on his fragile leg.

 "Today I drank half a liter of watermelon juice," said Yang, who is stumped by his unchanged weight. "By increasing my workouts and keeping with the juice diet, I hope I can reach my ideal weight of 63 kilograms."

The replacing of meals with fruit and vegetable juice might have a desired effect on the scales, but it can have a more damaging effect if maintained over a sustained period of time. 

"Choosing juice to replace a meal of staple foods is a healthy way to diet, but one cannot replace all foods with juice. Doing so can cause a nutritional imbalance," said Huang Yunyu, a nutritionist.

While talking about the effects of a juice diet, Ji Baoping, a professor at China Agricultural University and a specialist on the benefits of fruit nutrition, said that weight loss depends on how many different fruits and vegetables are mixed, and how long dieters can stick with the diet. "The [fruit and vegetable juice] diet is easy. All it involves is replacing one meal a day with juice, and trying to make the juice recipe as rich as possible," Ji said.  

Despite Yang's experience, there are many successful case studies that suggest drinking six cups of juice a day with only one meal can shed a considerable amount of weight. Pan Shiyi, a Chinese real estate tycoon and famous Weibo celebrity, brought the juice diet into the national spotlight this March.

"I have lost nine kilograms on the juice diet since last August," Pan claimed in March on his Weibo account. "My cholesterol level has dropped to normal and I even feel my eyes are brighter."

Pan replaced meals at both breakfast and lunch with juice, eating only a small portion of food for dinner.

Whether replacing two meals is better than one for the juice diet is as debatable as whether it actually improves your eye color, with no evidence to support either claim.

"The effect of this kind of fad diet is quick to see because it is probably the loss of sugar in the body and not fat that makes one lose weight. For this reason, such weight loss is unsustainable," said nutritionist Huang.

Huang opposes these quick-fix diets and believes dieters should only make slight dietary adjustments and keep regular workouts.

"The juice diet is effective, but you should not overdo it. Prolonged dieting by only consuming fruit and vegetable juices will cause substantial protein deficiency and a sharp drop in metabolism. Even by drinking six cups of juice daily, it can hardly meet one-third of your daily protein requirements," said Fan Zhihong, a nutrition expert at China Agricultural University. Fan added that protein deficiency is usually seen in symptoms like feeling cold, hair loss, edema (swelling of the legs) and anemia (lack of red blood cells in the body).

"A healthy weight control program should ensure supply of all essential nutrients," continued Fan. "It is possible to cut staple foods at dinner and replace them with an apple or serving of yogurt, but dieters should have a normal breakfast and lunch."

Sun Na contributed to this story.