For decades, we have been told that when it comes to losing weight, slow and steady is the way to go. “Rapid weight loss is unlikely to help you maintain a healthy weight long-term,” says the National Health Service (NHS) website. “And it comes with health risks.”
Losing weight any faster than 1kg a week has been linked to problems such as gallstones (because it upsets the balance of cholesterol in the body), malnutrition and fatigue due to the sudden drop in calories.
There is also the widely held view that crash dieters will put the weight back on more quickly because drastic food plans can’t be sustained long term.
But research is turning this advice on its head. Last month, an Australian study in the Lancet showed rapid weight loss was more effective in the short term than a gradual, sustained approach.
One group of obese adults were put on a 12-week rapid weight loss programme with meal replacements of 450 to 800 calories a day (an average man needs 2,500 calories a day to maintain his weight. For a woman, it’s 2,000 calories).
Another group was put on a gradual weight loss programme, cutting 500 calories per day.
More of those in the rapid weight loss group achieved the goal of losing 15 per cent of their weight.
When the researchers followed up the participants two years later, both groups had regained most of the weight they had lost. But there was no difference in how quickly they put it back on, which flies in the face of conventional thinking that losing weight too quickly means you’ll put it back on just as fast.
“The idea that losing weight slowly is better for you is an old wives’ tale,” says Professor Nick Finer, consultant endocrinologist and an expert in obesity at University College London Hospitals.
Here we look at other new thinking about weight loss:
CRASH DIETING IS A HELPFUL KICK-START
Concerns have been raised over what crash dieting does to the body.
“On a very low calorie diet, it’s unlikely you’ll be able to get five portions of fruit and veg a day or three portions of calcium,” says Sian Porter of the British Dietetic Association.
“This is why some obese people who go on drastically low calorie diets have been found to be suffering from malnutrition.”
But she says slashing your food intake can be helpful as a kick-start because fast results get you motivated. However, these kinds of diets should be followed for a maximum of only 12 weeks and with advice from a doctor.
“It can help initially, but it still needs to be combined with learning new habits, such as eating because you’re hungry and not for comfort,” says Jane Ogden, professor of health psychology at the University of Essex, who researches obesity.
EVEN YO-YO DIETING MIGHT NOT BE BAD
A longstanding worry about sudden weight loss is that it leads to yo-yo dieting — a cycle of slimming and regaining weight.
Some experts believe this is bad for the heart, because it struggles to cope with the sudden changes in calorie intake. But there is no evidence crash dieting or yo-yo dieting puts strain on your heart, says Michael Mosley, a doctor and author of The Fast Diet, which advocates intermittent fasting. “It might be a problem if you went on a diet without protein. If you do this, your body will start to cannibalise your muscles, and the heart is a muscle,” he says.
Another theory is that yo-yo dieting can slow the metabolism over time. The thinking behind this is that every time you lose weight, you lose muscle. When you regain weight, you put on fat, which burns calories more slowly.
But Michael Mosley says this is a myth. “There’s nothing wrong with losing weight rapidly, as long as you have adequate protein and nutrients, and exercise to maintain muscle,” he says. And weight loss, even if not maintained, can benefit the heart, a team at University College London reported earlier this year. They analysed data from more than 1,200 people and found adults who lost enough weight to drop a BMI category (from obese to overweight or overweight to normal weight) — even if the weight was then regained — had less furring of the arteries at ages 60 to 64 than those who had never lost weight.
REGAINING WEIGHT ISN’T LACK OF WILLPOWER
For many experts, the important message to take from the Australian study is not that rapid weight loss works best, but that however you lose weight, you are highly likely to put it back on.
And the problem is not lack of willpower, but that obesity makes it harder to shed weight.
“Despite what the government tells us, once your BMI is above 30 it’s difficult to lose weight and keep it off through diet and exercise,” says Guy Slater, a bariatric surgeon with Streamline Surgical. “This is the reason so many people end up having surgery. Many of my patients have lost weight through diet in the past and often have done very well, losing six stone and being slimmer of the year at their club. But they always regain it.’
Scientists believe that when you gain weight, the body is reprogrammed to behave as though this is their normal weight.
So when you cut calories, the body “thinks” it is starving and acts to stop the weight loss. Studies show that when obese people diet, they produce higher levels of the hunger hormone ghrelin and abnormally low level of hunger-suppressing hormones.
“We’ve evolved to defend our highest weight,” says Professor Finer. “It’s all very well telling people to change their lifestyle, but they’re fighting against biology. If you look at people who have had gastric surgery and need to have it reversed, within six months they are back to where they started.”
He believes the answer lies in appetite-suppressing drugs to help with weight loss maintenance once someone has slimmed down through diet.
STARVE TO HELP DIABETES AND BOOST IMMUNITY
Short-term, drastic calorie reduction can have benefits over and above shedding the pounds.
Reducing your daily energy intake to 800 calories can reverse type 2 diabetes in just eight weeks, research by Professor Roy Taylor, director of Newcastle Magnetic Resonance Centre at Newcastle University, United Kingdom has shown.
In the study, which involved 11 people, blood sugar levels returned to normal after the extreme diet.
At the end of eight weeks, the participants returned to a normal calorie intake, but with advice on healthy choices. Three months later, seven were free of diabetes.
It’s not that the speed of the weight loss does anything special for diabetes. “It’s that people find it easier to take a short-term approach and so they’re more likely to stick with it and achieve the weight loss they need,” says Professor Taylor.
Meanwhile, a study involving 5,000 people in the Lancet Diabetes and Endocrinology journal found that weight loss surgery can dramatically reduce the odds of developing type 2 diabetes — there was an 80 per cent reduction in cases of the disease in those who had the surgery.
And in January, the University of Southern California found that fasting — no calories for two to four days at a time — kick-starts stem cells in the bone marrow to produce white blood cells, regenerating the immune system.
They found fasting also reduced the enzyme PKA, which is linked to ageing, and a hormone thought to increase cancer risk.
SO WHAT IS THE SECRET TO KEEPING WEIGHT OFF?
How do some people manage to lose weight for good?
“It’s about reinvention,” says Professor Ogden. “You have to no longer see yourself as a fat person who’s lost weight, but as a slim, healthy person.
“The people I’ve worked with who have kept the weight off have become Weight Watchers group leaders, triathlon runners, gym instructors — it’s become a big part of who they are.”
Professor Taylor says writing down the reasons you lost weight and your present weight each week so you don’t let things slide can help, as can support from friends, family or a slimming club.
Dr Arabella Onslow lost ten stone three years ago.
“I have put a stone and a half back on,” she says. “No matter how you do it, it’s keeping the weight off that’s difficult. You have to focus and not take your eye off the ball.”
Professor Finer says the Australian study highlights the importance of prevention. “We should be helping people before they progress to obesity,” he says.
“If you went into a doctor’s surgery with a cigarette, they’d advise you to stop smoking. If you went in slightly overweight, no one would even bring it up.”