The diet in question requires obese people to consume just 530 calories a day for three months in a bid to shed excess pounds.
However, Professor Mike Lean, head of human nutrition at Glasgow University and a consultant physician at Glasgow Royal Infirmary, told Scotland on Sunday that the diet poses health risks and urged dieters to avoid such extreme low-calorie regimes.
"If people go on what amounts to a starvation diet - and just over 500 calories a day is close to a starvation diet - they may be liable to run out of nutrients in a relatively short period of time," he warned.
"You don't have to buy expensive products to lose weight and you certainly don't have to believe the hype. If people are tempted to try these schemes they should go and see their GP and find out what they can offer."
The professor claimed that eating two bowls of porridge, fruit and skimmed milk a day is as effective as the liquid regime and should avoid the risk of metabolic troubles posed by the latter.
A recent study also suggested that eating two eggs a day can help to promote weight loss when eaten as part of a calorie-restricted diet.