Liquid diets have had an image problem — the idea of losing weight by mixing sachets of powder into meal replacement milkshakes or soups makes dietitians very unhappy.
They worry that losing weight too quickly could be bad for you, and such plans don’t teach you how to eat healthily afterwards.
Indeed, many people do quickly put all the weight back on.
And then there are the pyramid-selling techniques behind some of these liquid diets, which have caused doctors to be especially cautious about making use of them.
But that poor image could be due a rethink following compelling new research suggesting low-calorie liquid diets can tackle obesity and reverse type 2 diabetes.
And it was backed by an editorial in the British Journal of General Practice last month.
James Aitken, a 60-year-old taxi driver from Wick in Scotland, is one who has benefited from this approach.
A year ago he weighed 26st — at 5ft 6in, his BMI was 56 — classifying him as ‘morbidly obese’.
He faced having to give up his job because his ballooning stomach was pressing into the steering wheel.
Meanwhile, his type 2 diabetes was getting to the point where he’d need to start injecting insulin.
This might have cost him his taxi licence because the Department of Transport does not recommend being on insulin and carrying paying passengers.
‘Even Lola, my labradoodle, was getting fat because I couldn’t take her for walks any more as my knees hurt too much,’ says James.
‘I longed to play with my grandson Cooper, who’s a toddler, but kneeling and getting up and down with him was impossible.’
Many doctors would have said that the only way for James to lose the 2½ to 5st needed to make a significant difference to his health was stomach-reducing surgery.
‘I was nervous of having the operation because of the obvious risks, but also because I’d heard that nearly half the patients have to go back for another one’ says James.
But he was lucky — his GP’s surgery was taking part in a trial funded by the Scottish government to test the effectiveness of a liquid diet called the Counterweight programme.
For three months, all your food comes in the form of a nutritionally balanced drink. Either fruit or savoury-flavoured, it supplies 800 calories a day.
‘It’s a bit of a shock for the patients to start with,’ says Mahri Swanson, the practice nurse at the surgery and part of the team supporting James and others in the trial.
She adds: ‘These are people who could have been eating 3,000-4,000 calories a day.
‘For the first few days they are really hungry. But, surprisingly, most quite quickly say it’s OK, and within a week aren’t craving food.’
By the end of his three months James had dropped a remarkable 6st, giving him a BMI of 43.5.
A year later he’s on a healthy eating plan and has not only kept the weight off but is heading for 19st with regular gym visits.
More important are the specific improvements in his health: his diabetes has been transformed — not only does he not need insulin, but his blood glucose is under control and he’s been able to stop two of the three diabetic drugs he was taking.
James did particularly well on the diet, but the trial’s results were pretty impressive, too.
According to the February issue of the British Journal of General Practice, about 30 per cent of the 90 people taking part lost 15 to 20 kilos and kept it off for a year with a lot of support.
Several Scottish health authorities are planning to make liquid diets available through GPs as a result.
Professor Mike Lean, chair of human nutrition at Glasgow University and a lead researcher on the trial, is having discussions with Diabetes UK about funding for a larger controlled trial of 200 people to properly test the diabetic benefit.
‘The rising number of people who are obese or diabetic is going to cost billions,’ says Professor Tony Leeds, an obesity specialist who runs a clinic at the Central Middlesex Hospital in London and has been treating patients with liquid diets for years.
‘If these results are repeated, the savings could be huge.’
There are other benefits, too — James’s knees are also feeling a lot better.
‘Lola’s delighted, too, because we are going for walks again and afterwards I even have the energy to play with Cooper,’ he says.
Indeed, in Denmark a liquid diet is about to become the first-line treatment for people with osteoarthritis of the knee.
This follows a study which found that when 175 osteoarthritis patients were put on a liquid diet they not only lost a lot of weight, nearly all of which was fat, but more than 60 per cent also showed significant improvement in pain and disability.
‘Until a few years ago all that was on offer for these patients was painkillers and advice to lose weight that rarely worked for long,’ says Professor Henning Bliddal, a rheumatologist at Frederiksberg Hospital who led the study.
‘Osteoarthritis normally makes bones weaker by reducing bone mineral density.
‘But the bones of patients on the liquid diet improve, possibly because it contains the recommended daily allowance for all amino acids, fatty acids vitamins and minerals.
‘This means they get extra vitamin D, which is vital for building bones.
‘About ten per cent of people over 55 have bad knees and are overweight, and the diet has changed the way we treat them,’ adds Professor Bliddal, who is running a trial to test the possibility that it can improve the structure of damaged cartilage in the knee.
The Danish study, published in the European Journal of Clinical Nutrition in 2011, concluded that the liquid diet was ‘effective and safe’.
In fact, despite concerns that a rapid drop in calories might be bad for you, emerging evidence suggests it may lower cholesterol levels.
Some researchers have even suggested it might even reduce asthma symptoms.
But whatever calorie restriction regimen — diet or liquid diet — it’s clear that a supportive and effective follow-up programme to make sure that the weight stays off is vital.
This has been a key part of the Scottish trial.
And it’s the special focus of the Rotherham Institute for Obesity, which over the past three years has helped the local population of 250,000 lose 17 tons between them — and halved the weight loss surgery rate in the first year (30 fewer patients have had the surgery, saving around £300,000).
The institute takes 2,000 referrals a year.
‘Our team of dietitians, fitness experts, psychologists and cooks make sure they have a good chance that any weight they have lost stays off,’ says Dr Matthew Capehorn, who heads the scheme and is also clinical director of the National Obesity Forum.
Under official guidelines from the National Institute for Health and Clinical Excellence (NICE), low-calorie diets are available on the NHS for people ‘who are obese and have reached a plateau in weight loss’.
The hope is that the new evidence will give GPs more confidence to use them.