8 Myths About Dieting

 8 Myths about dieting from the article by Michael Mosley in The Times. 

On my first day at medical school a hundred of us gathered in a lecture theatre to be greeted by the Dean. He talked for an hour but there are only two things he said that I still remember. The first was that, based on previous experience, four of us in that room would marry. He was right; I met my future wife that day.

The other thing he said was that while we would learn an enormous amount over the next 5 years, within 10 years of graduating much of what we had learnt would be out of date.  Medicine is constantly changing and unless you keep up you are doomed to cling to outmoded ideas.

This is particularly true in the field of human nutrition and dieting. So what are some of the most common and firmly held dieting myths?

Claim 1 Eating breakfast is important if you want to avoid putting on weight.

We are often told that eating a good breakfast is a simple way to control your weight. If you skip breakfast then you will get hungry later in the day and snack on high calorie junk food. Eating breakfast revs up your metabolism, preparing you for the day.

It seems a plausible suggestion but is it true?

There have certainly been plenty of studies which have compared people who skip breakfast with people who don’t and the breakfast eaters are often found to be slimmer and healthier. This could be for the reasons stated above, or it could be that breakfast skippers are generally less healthy individuals and the fact that they are a little bit fatter has little to do with when they decide to break their fast.

One way to test the merits of these claims is to take two groups of people, breakfast skippers and breakfast eaters, and make them swop habits. Get the breakfast skippers to eat breakfast and vica versa.

In a recent study, “The effectiveness of breakfast recommendations on weight loss: a randomized controlled trial”, http://ajcn.nutrition.org/content/early/2014/06/04/ajcn.114.089573.abstract, researchers did just that. They got 300 overweight volunteers and asked the breakfast skippers to eat breakfast, while those who routinely ate breakfast were asked to skip breakfast for the duration of the trial.

They weighed the volunteers beforehand and then at the end of 16 weeks. There was high compliance with the new regimes, so what actually happened?

Well, the breakfast skippers who had made themselves eat breakfast lost an average of 0.76kgs. That is not a huge amount, but it is consistent with what breakfast advocates might expect.

Except that the breakfast eaters, who had spent 16  weeks skipping breakfast, lost an almost identical amount, an average of 0.71kgs.

The researchers concluded that, contrary to what is widely believed, a recommendation to eat breakfast  “had no discernable effect on weight loss in free-living adults who were attempting to lose weight”.

 A similar randomised study done years ago, but with smaller numbers, came to a similar conclusion. The researches thought that making people change their habits was what made the difference, or as they put it “those who had to make the most substantial changes in eating habits to comply with the program achieved best results”.

I like breakfast, it is one of my favourite meals to the day, and I certainly think that children should eat breakfast. If you want to keep fuller for longer then the evidence is clear that you should eat a breakfast that is rich in protein, like eggs, ham or fish, rather than sugary cereals or toast. Protein is more satiating than carbohydrates.

If you are one of those who don’t like eating breakfast and who, perhaps, find that eating breakfast first thing makes you hungrier, then there seems no compelling scientific reasons to do so.

• Claim  2:   It is important, before you start dieting, to set realistic weight goals. Otherwise you will become frustrated and give up.

Again, this seems like a reasonable assumption. But is it right? A recent review article titled Myths, Presumptions and Facts about Obesity in the prestigious medical journal, The New England Journal of Medicine, put this claim firmly into the “myths” category.

As they point out, “several studies have shown that more ambitious goals are sometimes associated with better weight-loss outcomes”. In one of those studies, “Weight loss goals and treatment outcomes among overweight men and women”,  nearly two thousand overweight men and women were asked about their goals before they started on a weight loss programme. They followed them for 2 years and found that, with women, “less realistic goals were associated with greater weight loss at 24 months”. For men there was no link, one way or the other, between how realistic their goals were and whether they succeeded.

• Claim 3   It is better to lose weight slowly and steadily, rather than rapidly

This is another of those claims that seems to be self-evidently true but which the  obesity researchers behind Myths, Presumptions and Facts about Obesity describe as a myth. Or as they put it, “Within weight-loss trials, more rapid and greater initial weight loss has been associated with lower body weight at the end of long-term follow-up”.

Very-low-calorie diets (VLCDs), based on consuming less than 800 calories a day, have been used since the 1970s to induce rapid weight loss, but the assumption is that once you stop you will simply put it all back on. In a thorough meta-analysis, The evolution of very-low-calorie diets: an update, reviewers looked at the results of 6 randomised trials that had run for at least a year comparing very-low-calorie diets with standard low-calorie diets.

They found that the VLCDs led, not surprisingly, to much bigger weigh loss in the short term and though the dieters did, on average, later put back on much of the weight they had lost, so did those on the standard diet. In the long term there didn’t seem to be any significant difference between these approaches. The researchers point out that doing VLCDs can be more expensive but that “Cycles of weight loss and regain do not seem to have the adverse health and metabolic consequences once feared”.

An interesting recent development is the use of VLCDs (600 calories a day over several weeks) to try and improve blood glucose control in overweight type 2 diabetics. A small trial in Newcastle produced very positive results and larger trials are planned.

• Claim 4. It is better to eat several small meals a day rather than a couple of large ones.

A common belief is that if you spread out your food into lots of small meals this will increase your metabolic rate, keep you less hungry and help you lose weight. In a recent study researchers at the Institute for Clinical and Experimental Medicine in Prague decided to test this idea by feeding two groups of type 2 diabetics meals with the same number of calories but taken as either two or six meals a day.

Each group ate around 1,700 calories a day. The group eating two meals a day ate their first meal between 6:00am and 10am and their next meal between 12pm and 4pm. The others ate at regular intervals throughout the day. Despite eating the same number of calories the “two meal a day” group lost, on average, 1.4kg more than the snackers and about 1.5inches more from around their waists.

What was also surprising is that the volunteers eating their 1700 calories spread out as 6 meals a day felt less satisfied and hungrier than those sticking to the two meals. The lead scientist, Dr Kahleova, believes cutting down to 2 meals a day might also people without diabetes who are trying to lose weight.

• Claim 5. when you stop eating for a while your metabolic rate slows down as your body tries to conserve your fat stores.

Fear of going into “Starvation mode” is common and yet, at least from an evolutionary perspective, it makes little sense. Our remote ancestors often had to go without food for a while and if, every time this happened, they had simply curled up on the floor of their cave and waited for pizza to be delivered they would have gone extinct. Only during periods of prolonged famine would it make sense to slow the metabolism down, wait for better times to come.

The myth seems to be based, in part, on the Minnesota starvation experiment, a study carried out during World War Two in which young volunteers lived on extremely low calorie diets for up to six months. The purpose of the study was to help scientists understand how to treat victims of mass starvation in Europe.

After prolonged starvation there was a drop in body temperature and heart rate, suggesting that their basal metabolic rate (the energy burnt by your body when you are at rest) had fallen. This, however, was an extreme situation.

A more recent experiment on the effects of short term calorie restriction, Resting energy expenditure in short-term starvation, produced very different results. In this experiment they took 11, healthy volunteers and asked them to live on nothing but water for 84 hours.

The researchers found that the volunteers’ basal metabolic rate went up while they were fasting. By day 3 it had risen, on average, by 14%.

One reason for this may have been the significant rise they detected in a catecholamine called noradrenaline, which is known to burn fat.

If they had continued then, I’m sure, the volunteers’ metabolic rates would eventually have fallen, not least because they would have begun to lose significant amounts of weight. But, certainly in the short term, there is no evidence that starvation mode is anything other than a myth.

• Claim 6.  If you stop eating for a while then your blood sugar will fall dramatically and you will faint.

In the trial I mentioned in the previous post, Resting energy expenditure in short-term starvation, they also measured the volunteers’ blood glucose levels. They found that their blood glucose levels did slowly fall over the three days, from 4.9mmols/l on day one to 3.5mmols/l  by day 4.  These, however, are the sort of levels you might expect to see in a healthy individual who had their blood taken before breakfast . They are not, in any sense, abnormally low.

At the same time the levels of fatty acids in their blood shot up, showing that their bodies had switched into major fat burning mode.

Your body evolved to cope with periods without food. Modern humans, however, are used to eating lots of regular meals and there is evidence that the hunger hormone, ghrelin, rises simply in anticipation of a meal. Intermittent fasting can be tough, but there is no evidence it is will cause you to faint

• Claim 7. Juicing is a good way to lose weight.

There are juice diets out there promising that you can lose “7lbs in 7 Days”, but are they credible?

Let’s start by looking at some of the numbers. There are around 3500 calories in a lb of fat and the average woman consumes 14,000 calories a week (2000 a day). So if you ate nothing at all for a week and lost all your weight as fat (which you won’t), then the absolute maximum amount of fat you could lose is 4lbs.

So why do the scales sometimes drop far more than that? Well, excess glucose is stored in your muscles and liver in a form called glycogen. This also binds water. When you stop eating your body burns through the glycogen stores, releasing the water. After a week you may well have lost 7 lbs but much of that weight will be water, and also some muscle, since, on these diets. you’re eating little or no protein.

The body doesn’t store protein, so after 24 hours without it in your diet your body will start to cannibalize itself. Not surprisingly, once you start eating normally again your body will replenish its water and glycogen stories and much of the weight will come back on.

Claim 8 Drinking 2 litres of water a day will help you lose weight.

This myth dates back to the 1940s when researchers calculated that 2 litres was how much water someone’s body used in 24 hours. However, the researchers also said (and this gets ignored) that we obtain much of the water we need each day from our food. Drinks such as coffee and tea also count, despite what many people believe.

Drinking eight glasses of water a day could help you lose weight if you drink it very cold. Drinking ice-cold water burns through a few calories simply because you have to raise that water to body temperature. Drinking lots of water will also mean you have to get up from your chair more often to go to the loo, which has to be a good thing.

Water can help you lose weight, if it comes in the form of soup. If you drink water with your meal (a bit of chicken and a few vegetables) then the food will be kept in your stomach for digestive juice to do their bit, but the water passes straight through the stomach and into the intestines, where it is absorbed. Drinking water has very little effect on how hungry you feel a couple of hours later.

Ultrasound and MRI studies have shown, however, that if you take the chicken and vegetables and blend them with the water then the stomach will stay fuller for longer, staving off hunger pangs.

In head to head comparison studies, volunteers eating soup reported feeling full for up to an hour-and-a-half longer than when they ate the same calories, but consumed as food and water. .

Source: https://thefastdiet.co.uk/forums/topic/food-thought-fast-day-losing-weight-drinking-water/