Why crash dieting DOES work: Surprise evidence suggests it's the best way to slim



Here's a sobering thought: beach weather is nearly here, and the diet you've been meaning to embark on since January remains in the planning phases.

You really don't want to expose those extra pounds to the world, but you do want to put on your swimsuit and feel OK about it. A crash diet seems to be your only option, but aren't crash diets unhealthy - not to mention ineffective - after the first week? Not if you approach them correctly.

Despite what many nutritionists have preached for years, low-calorie diets can be healthy if you do them right, and can work wonders on pounds and inches in just a few weeks.



An apple a day...: Choosing the right food for a crash diet can help the pounds drop off

Clinical experience shows that somebody with a serious commitment to weight loss can lose up to 20 pounds - and two to three dress sizes - in two months. That's a lot of weight, and an enormous change in appearance for most of us.

Best of all, if a crash diet is done right (and you make permanent changes to how you eat) it can yield results that will stand the test of time just as well as those slow and careful, long-term diets that emphasise depressingly incremental drops in weight.

Conventional wisdom says that rapid weight loss leads to rapid weight regain, but a new generation of science is showing that slow isn't necessarily better.



In fact, fast weight loss - if achieved with a healthy, caloriecutting food-based diet - can bring long-term success equivalent to the more gradual weight-loss programmes, which is reason for procrastinators everywhere to rejoice. In fact, for some people, healthy crash dieting may work even better than a diet that lasts all year.

A recent study from my laboratory at Tufts University in Boston, Massachusetts, found that the slow and careful approach seems to be sustainable only by those dieters who are not sidetracked by rich food, party snacks and other common food challenges in daily life.

So where does exercise fit into all of this? The drumbeat of get moving to lose weight has become so loud that almost everyone blames his or her weight problem on not spending enough time working out.

The food we are putting in our mouths seems to take a back seat.

But a look at the evidence doesn't support the hype.





'Exercise doesn't necessarily make you thin'



Shedding the pounds: Studies show that exercise is not the key factor in weight loss

National surveys show that people who do manual jobs - construction, farming and domestic work - are often heavier than people who sit in front of a computer screen all day.

Indeed, physically strenuous jobs carry a 30 per cent increased risk of obesity in the U.S. when compared with office jobs.

Of course, comparisons like this don't factor in social class, or whether you eat chocolate or take a run after work, but that's the whole point - compared with factors like what we snack on, hard manual labour just doesn't make as much of a difference.

Even if your day is spent shovelling gravel, you're still going to develop a pot belly if you lunch on pizza and fizzy drinks every day.

This is not to say exercise is bad - exercise is, of course, important for maintaining health, strength and vitality. But when it comes to weight loss, it doesn't seem to be the panacea that it is often made out to be. And the evidence isn't just anecdotal.

My laboratory summarised 36 years of published studies on exercise and weight, conducted between 1969 and 2005, and found that adding even an hour of exercise per day results in an average fat loss of just six pounds over the course of several months - hardly the benefit one would expect from all that work.

Perhaps more importantly, most of the studies managed to get people to exercise only 30 minutes a day, at which point the average weight loss goes down to three pounds. One research study in The Netherlands also highlighted the problem that simply starting and sticking with a serious programme of exercise is easier after you've lost some weight.

Men and women ranging from thin to slightly overweight volunteered to train for a half-marathon in a study lasting 40 weeks.

Secrets and lies Only 34 per cent of women tell others when they are dieting and around a third lie about their dress size

The heavier subjects within this group were only slightly overweight, but even so, they were the ones who dropped out before the training was halfway through. It's not that the overweight people were lazy, just that exercise is much harder if you are carrying around even 20 excess pounds - the equivalent of a large backpack full of textbooks - while you do it.

Which brings us back to dieting and how to make it really work and, in particular, how do you avoid common concerns like weight-loss plateau (when the body adapts to the lower calorie intake and slows down the metabolism accordingly)? The answer is simple: by cutting enough calories.

Many popular diets don't cut as many calories as is needed, because they don't deal with the hunger factor well enough to go further.

These diets do achieve short-term weight loss with a combination of small calorie cuts and low-sodium meals that cause water excretion, but once water balance stabilises, you begin to feel like your dieting is getting nowhere.





'Eat the right food at the right time'



The first principle of successful dieting is to get calories low enough to cause ongoing, serious fat loss. In practice, this means getting daily calorie intake down to 1,200 calories a day if your starting weight is 8.5 to 11 stone, or to 1,800 a day for those weighing 14 to 17 stone.

Several studies have shown that at this level of intake, calorie requirements don't decrease anywhere near enough to make your weight plateau, meaning fat continues to be pulled from fat cells and real weight continues to slide off.

The second principle involves eating the right foods at the right time; if you don't, counting calories won't cut it because you will be too hungry or unsatisfied to see it through.

Based on research studies, it's clear that liquid calorie diets - from meal replacement drinks like Slim-Fast - do work, but they are so desperately boring that few people can stick to them.

To enjoy yourself more, go the real-food route and maximise benefits by ensuring every meal and snack you eat combines at least two of the properties that numerous research studies have shown cut hunger and increase the feeling of being full: high fibre, high protein, high volume and low glycaemic index carbs.









And keep those good foods coming. My experience of helping people lose weight showed that eating three meals and two to three snacks every day and spreading calories evenly from morning to night is about as important as choosing the right foods when it comes to suppressing hunger.

What about even faster weight loss? You know those diets: the ones that promise to dissolve 21/2 stone from your belly in one month, or a stone in four days. Unfortunately for anyone longing for results by next weekend, such diets are pure snake oil.

Crash dieting can work, but there is a threshold. It's a physiological fact that the human body is capable of losing only a maximum of about three pounds of actual fat per week, even if you eat nothing at all.

Greater weight losses than this might occur for a week or two if you put yourself through the wringer of fruit juice fasts, purges, or harsh detox programmes, but you won't lose any more fat - just water, intestinal contents and sometimes muscle. That's the kind of weight that will bounce right back after a good party or two.

The bottom line is that regular workouts are great for health and strength, but if you want to lose weight, the really important thing is what you eat.

Stock up on the good foods that help with weight control, and then keep those calorie counts down to make weight loss a reality this time.

Start now, and there's still time to put your new body on a collision course with summer.