Long before there was the Atkins, the Dukan or the paleo, there was one diet favoured by anyone looking to lose weight fast: the liquid diet.
he 20th century had its fill of them: the cabbage soup diet (which promised a hearty detox and fewer than 100 calories per bowl), the apple cider vinegar diet (when sipped before every meal, it nixed your appetite and stripped your tooth enamel)… even the milk diet, whereby followers down four pints of semi-skimmed a day.
But then in 1988, chat show host Oprah Winfrey announced she had lost 67lbs by drinking Optifast, a ‘meal replacement’ shake, and celebrated by dragging a wagon full of that much fat across her studio set.
Now, ultra-low calorie soups and shakes have been pulled out of the diet archives and are being touted as an effective way to rapidly lose weight and even reverse diabetes, which studies show can increase the severity of a bout of coronavirus.
In the UK, from this week, soups and shakes will be available free on the NHS after research showing that half of type 2 diabetics placed on an 12-week, 800-calorie diet were in remission a year later.
This is somewhat of a U-turn from the typical NHS diet plan for weight loss, which recommends 1,400 calories a day for women and 1,900 for men – leading to a loss of one to two pounds a week.
The rapid weight loss from liquid diets can have a powerful psychological effect on slimmers, says Kim Pearson, a London-based nutritionist. “[Rapid weight loss] is 100pc good for motivation,” she says. Her Harley Street practice recommends Proteifine meal replacement products, which deliver between 800 and 1,000 calories a day, and can lead to weight loss of around a stone a month.
Pearson believes that a few months away from a conventional diet can be effective because it helps to “reset” behaviour patterns and stop clients constantly thinking about eating. “It’s kind of like food rehab,” she says.
Debbie Kersey (58) agrees. “It stops you thinking about mealtimes,” says Kersey, who lost two and a half stone using Exante shakes, recommended by her doctor as a treatment for her type 2 diabetes.
Kersey has been dieting since she was 14, but says that only by using the low-calorie shakes could she prevent cravings for unhealthy food. She’s not the only one – bizarrely, very-low calorie liquid diets can leave followers feeling less hungry than if they steadily cut down on portion sizes.
There is not yet solid evidence as to why that might be the case, but Professor Francesco Rubino, a consultant bariatric surgeon at London Bridge Hospital, has a theory: very-low calorie diets – as few as 800 kcals per day – whether in soups, shakes or whole food, have a similar effect on the body as a gastric bypass.
He explains that bariatric surgery is not just effective by reducing the size of the stomach, it also disrupts the body’s attempts to make you regain the weight by increasing hunger and decreasing fullness. This happens because the part of your gut responsible for creating these signals is bypassed surgically: it is no longer stimulated, and so stops telling your brain that you are hungry.
With very-low calorie diets, Rubino believes the same thing is happening: the gut is not being constantly stimulated by food passing through and, in its resting state, does not create feelings of hunger.
Dr Michael Mosley, the BBC broadcaster and creator of the 5:2 Diet, points to a 2018 study, which compared the effects of a meal replacement programme of around 800 calories a day to those using traditional NHS weight loss programmes. Those who followed the low calorie diet were 10.7kg lighter a year later, three times more than in the other group. They also had much better reductions in risk of diabetes, heart disease and stroke.
However, these diets need to be followed with caution. They are most suitable for those who have a lot to lose already and would be a no-go for anyone with a history of eating disorders. What effects these diets might have on the body in the years to come are still unclear, says Rubino. “We simply don’t know what will happen over the long term.”