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Dieting

MagazineFebruary 2000 (Vol. 10 Issue 11)Dieting

Dieting is prone to potentially dangerous fads and fashions

Dieting is prone to potentially dangerous fads and fashions. In our second Millennium issue, WDDTY exposes the worst of the slimming regimes and offers proven ways to reach your ideal weight.

Nobody agrees on the best way to diet. The proof of that is the number and variety of diet books which reach the bestseller list. One year, we hear that we're supposed to eat carbohydrates in abundance and cut down on fat; the next year, carbohydrates are out of favour, but gobbling up fats and protein is now considered the definitive solution. The other indication is the size of the audience for these books, usually comprised of people who are multiple diet failures, constantly on the look out for the one diet which will finally conquer their battle of the bulge.

As all of us have no doubt overindulged in the Millennium celebrations, WDDTY asked three top nutritionists Dr Marilyn Glenville, Dr John Briffa and Udo Erasmus, author of Fats that Kill, Fats that Heal (see Second Opinion, back page), to suggest the best ways to lose weight. These nutritionists, who have helped many people to control their weight, debunk many of the greatest diet myths and expose the dangers of many of the most popular fad diets.

Dr John Briffa

Myth no 1: Dieting is a matter of counting calories and eating less.

The widespread belief that a reduction in food consumption is a prerequisite for weight loss is based on the calorie principle of dieting. This principle was first put forward in 1930 by two doctors, Newburgh and Johnston, at the University of Michigan, US. Their theory was that if we consume fewer calories than our body burns, we are bound to lose weight. For instance, if our body burns, say, 2,500 calories in a day but we consume only 1,500, then a 1,000 calorie deficit results. To compensate, the body burns stored fuel to make up for this energy shortfall, and weight is therefore lost. Since the 1930s, the medical profession has adhered to the idea that calorie reduction is the only effective way to lose weight.

Although apparently sound in theory, the calorie principle is dangerously simplistic. While calorie restriction will almost certainly produce some weight loss initially, this loss can be virtually unsustainable due to a variety of physiological and biochemical factors. Despite the medical profession's attachment to calorie based dieting, no studies exist to suggest that it is effective for long term weight loss at all.

The speed at which the body burns fuel is referred to your "metabolism". Apart from the thyroid, metabolism is also affected by other factors such as exercise and food. To understand how food affects our metabolism, it is useful to think of the body as a sophisticated furnace, where the fire in the furnace represents the body's metabolism, and the fuel of the fire represents food.

Anyone cutting back on the amount of food he eats is likely to lose weight initially. After all, if we leave a fire without adding more fuel to it, the existing fuel gets burnt. However, eventually the flames go out, and all we're left with is a few dying embers. The fuel burning capacity of the fire is now greatly reduced. It's just the same in the body. When calories are restricted, the body soon becomes wise to the fact that food is in short supply, and so it does its best to conserve any existing stores of energy. In effect, the body adjusts itself to the reduced supply and adapts by burning progressively less fat.

Some dieters think that skipping meals and going hungry must be the best way to lose weight. But again, thinking for a moment about the fire inside us, if we light a fire at breakfast and don't fuel it in the middle of the day, by the time we come back to the fire in the evening, the flame will be so low that the fuel we put on it in the evening will not burn easily at all. Skipped meals mean that our body is more likely to store subsequent meals at fat. The real problems start once we increase our fuel intake again. Put more fuel on a fire that is almost out and it's likely that it will not burn at all well. There's a good chance that some of the fuel will end up unburnt. In the body, unburnt fuel tends to stick around as fat.

In one study, rats were examined as they gained and lost weight. Each time these rats lost and regained weight, their metabolism progressively slowed, The weight loss in the second cycle was half as fast as it was in the first, and the weight came back three times as quickly (Physiology and Behavior, 1986; 38: 459-64). Although this was only an animal study, this effect has also been confirmed in humans (JAMA, 1988: 26091: 47-50).

Severe calorie restriction forces the body to use not only fat to make up for the energy deficit, but protein as well. The protein the body uses as a sort of top up fuel comes from muscle. Muscle is essentially the body's engine house, and this is where the bulk of the body's fuel is burnt. If we lose muscle bulk our overall capacity to burn fuel declines. With this comes an inevitable decline in our ability to lose weight and an increase in the chances that we will put it on.

During a diet, food quantity generally declines. There is almost an inevitable reduction in our intake of nutrients. The reactions that burn food for energy are dependent on the supply of certain nutrients, such as magnesium and the B vitamins. For efficient fat burning potential it is important that we keep up our intake of a wide range of essential nutrients.

Another potential pitfall of low calorie dieting is that there is a tendency to become focused on the calorific content of foods, rather than their health giving potential. To lay down food as fat, the body has to put a bit of energy in. For the body to take 100 calories of fat and lay this down as fat in the tissues, only 2 1/2 calories must be expended. However, converting carbohydrate or protein into fat requires much more biochemical processing, and therefore more energy must be expended as a result. In fact, to convert 100 calories worth of protein or carbohydrate into fat, the body needs to expend 23 calories, almost 10 times the amount needed to process the equivalent amount of fat. Even if calorie intake is the same, a high fat diet is more likely to lead to weight gain than a high carbohydrate or high protein diet.

Myth no 2: You can lose weight on special diet foods.

The supermarket shelves are awash with products claiming to be "diet", "lite" and "low fat". The reality is that few of these foods actually deliver on this promise, and the only place they're likely to leave you feeling lighter is in the purse or wallet.

I recently took a trip around my local supermarket to see what was in store for the unsuspecting slimmer. I picked up a loaf of slimmer's bread, which boasted "only 28 calories per slice". Actually, weight for weight, this bread has no fewer calories than standard white bread at all. The reason that it has only 28 calories per slice is because the slices are pitifully small.

Another product I chanced upon was a slimmer's minestrone packet soup. This soup contained 59 calories per serving, while its non slimming version contained 95 calories. Interestingly, weight for weight, the slimmer's soup actually contained more fat than its non slimming version, and their ingredients were virtually identical. So now did the manufacturer managed to reduce the calorie content of their product? By reducing the serving size, from 25g to 15g. Oh, and just in case you're wondering, the pack prices were identical.

Myth no 3: To lose weight, you must stick to three small meals a day and avoid snacking in between meals.

A central theme in many weight loss regimes where calorie restriction is an integral factor is that three meals should be eaten, but snacks should be avoided in between. The principle here is that snacking between meals justs ups the calorie intake for the day and therefore could not possibly help in weight loss. In fact, it turns out that just the reverse is true. Eating in between meals can actually speed weight loss because it helps to keep that fire going inside. In one study, rats were given an amount of food during a one hour period each day. A second group of rats were given the same type and amount of food, this time divided into six feeding sessions throughout the day. The first group of rats tended to become overweight, but the second group did not. This is a very clear demonstration of the fact that "grazing" food throughout the day can actually help weight loss.

In another study, human volunteers were split into two groups. One group was given a certain amount and type of food as three meals over the course of a day. The other group was given exactly the same type and amount of food, but this time it was divided into seventeen snacks during the day. After only two weeks, the subjects on the grazing diet had significantly lower levels of cholesterol in their blood stream. The levels of insulin were also lower in this group, which is particularly relevant as insulin stimulates the production of fat in the body (N Eng J Med, 1989; 321: 929-34).

Marilyn Glenville:

Myth no 4: Dieters can control their cravings by willpower alone.

Most dieters experience cravings to a lesser or greater degree. Sugar cravings are caused by fluctuating blood sugar levels. The other cravings could be caused by a food allergy or perhaps a yeast problem (see the WDDTY Allergy Handbook). Ironically, if we are allergic to a particular food, we tend to crave it and eat it more.

By and large you can control your own cravings by eating complex carbohydrates regularly, avoiding refined food, especially sugar, and reducing foods and drinks that are stimulants.

There are two types of carbohydrates: complex and simple. To maintain well balanced blood sugar levels, you should eat foods containing complex carbohydrates, which give a slow rise in blood sugar and keep a constant level for about three hours, then eat again and prevent the level from dropping. Spacing food at three hourly intervals in this way is a proven solution to the battle with cravings.

Carbohydrates are a large group of foods that include sugars and starches. They are an important source of energy and the body breaks them down into the simple sugar, glucose. It is the slow speed with which this happens that is important in keeping blood sugar constant.

Complex carbohydrates give a slow release of energy because it takes time for the digestive tract to break them down into simpler substances that the body can use.

Complex carbohydrates include grains (wheat, rye, oats, rice, barley, maize); pulses (lentils, chickpeas, kidney and aduki beans); vegetables, including potatoes; and fibre in grains, beans and vegetables.

To help maintain a steady blood sugar level, aim to eat complex carbohydrates as part of your main meal and also as snacks during the day. You do not necessarily need to eat great amounts sometimes just an oatcake can be enough between meals to keep eating urges at bay.

If you find the symptoms associated with low blood sugar are greatest first thing in the morning, or you wake during the night, heart pounding and cannot get back to sleep, then it is very likely that your blood sugar level has dropped overnight and adrenaline has kicked into play. Eating a small, starchy snack, like an oatcake, one hour before going to bed and, if possible, one hour after getting up will help to alleviate these symptoms.

Make sure your complex carbohydrates are unrefined, which in general means choosing brown instead of white.

Carbohydrates with fibre in it also help to lose weight. It was originally thought that fibre's role was only to speed up the passage of food residues to prevent constipation. It is now known that some forms of fibre can actually slow down the absorption of sugars and help to maintain our blood sugar balance. Without fibre, food will affect the blood sugar level more quickly, and it is harder to eliminate the food residues. The food stays in the body longer, which means it absorbs more calories, so preventing you from shedding those kilos.

The simple carbohydrates honey, white and brown sugar, and glucose in high energy drinks are all refined foods and should be avoided.

Although fruit contains fructose (fruit sugar) which is a simple sugar, the fibre content of the fruit is a complex carbohydrate, which slows the digestion rate.

So fructose is acceptable when taken in the whole fruit, like an apple, but not when used in the refined form of powdered white fructose, which is bought in boxes.

Pure fruit juice can also cause a rapid change in blood sugar levels because it is not buffered by the fibre that is normally present. It is better to dilute fruit juice in water to make it less concentrated.

The brown is best theory doesn't apply to sugar: all colours do the same damage to your blood sugar balance.

The latest theory in nutrition is the Glycaemic Index, which has an important impact on blood sugar balance. Some carbohydrates have a "fast releasing" effect, while others are "slow releasing", and it has been found that this releasing effect can

be measured against glucose. This method of measuring has become known as the Glycaemic Index (G1). As glucose is the fastest releasing carbohydrate, and raises insulin to the highest level, the Index gives it a score of 100 everything else is measured against this score.

It is known that raised insulin levels encourage fat to be stored in the body. But if you have high insulin levels because your blood sugar keeps fluctuating, you will not only change more of your food into fat, you will also stop your body breaking down previously stored fat. In effect, it's a bit like adding money to your bank account without spending any: fine with cash, but not with fat. No wonder they are called "fat deposits"!

It is therefore important to optimise insulin levels and keep fat storage to a minimum. Whole foods, such as brown rice, are important because the fibre contained naturally in the food slows down the release of sugars and gives them a lower GI. The same goes for fruit rather than fruit juice, because of the fibre content of the fruit.

The most important confirmation that has come out of the Glycaemic Index is that it is beneficial to combine proteins and carbohydrates at the same meal. The idea of combining protein and carbohydrates makes sense and has been practised for centuries in traditional cultures where a meal would automatically contain foods such as lentils and rice.

The Japanese, for example, often have rice, fish and soya at each meal, along with vegetables. It was virtually unheard of to see an overweight Japanese person until the introduction of the Western diet in Japan.

The presence of protein in food (either animal or vegetable, such as tofu) actually lowers its Glycaemic Index. Pulses such as lentils, which naturally contain both protein and carbohydrate, have a low Glycaemic Index.

Food combining diets can be very helpful for people with digestive problems such as indigestion, but can actually make things worse for those with blood sugar imbalance.

The recommendation is that we eat foods that have a Glycaemic Index of around 50. Foods over 70 should be kept to a minimum or mixed with low GI foods.

However, as fascinating as the GI Index is, it would not be a good idea to swap one set of restrictive numbers (such as calories) for another. Instead, it's a good idea to make yourself aware of those foods that have the highest GIs and eat them in moderation (see box, p 3).

Myth no 5: A high protein diet which includes low calorie dairy produce is a good way to lose weight.

A certain amount of protein is essential. It is necessary for the structural formation of our bones, skin, hair and muscle. However, it is important to monitor our intake of protein to ensure that we are not only getting the correct amount but also that it is coming from the healthiest sources. Excess protein has been linked to kidney stones, gout and high blood pressure.

An interesting study in 1996 by the Harvard School of Public Health looked at protein consumption and increased bone fractures in women aged between 30 and 55. The researchers found that women who ate more than 95 g (3.4 oz) of animal protein a day had a increased risk of forearm fractures over women who ate less than 68 g (2.4 oz) per day. No increased risk was found for those women who ate vegetable rather than animal protein (Amer J Epidemiology, 1996; 143: 472-9).

Dairy products such as cheese, milk and cream should be used sparingly as they contain the protein casein. Casein is 300 times higher in cow's milk than it is in human milk, therefore it is hardly surprising that many people find it indigestible. While its casein richness is important for the fast development of large bones in calves, it can make some people quite unwell. The human digestive system is not designed to receive cow's milk.

The cow has a four stomach digestive system which deals with the casein easily. We humans with our different digestive tract cannot easily absorb the casein, so products like milk remain undigested in the gut and begin to putrefy and rot. It clings as undigested matter to the lining of the intestines and prevents the absorption of vital nutrients by the body.

Your body will use much more energy to digest foods that don't suit you. Most people can digest small amounts of milk quite adequately, but if you feel tired after eating, may be worth checking whether your meal contained a lot of milk perhaps in the form of things like custard or sauces on vegetables. If your body cannot digest food efficiently, it will find it harder to shift the excess weight you have and can even cause you to put on weight.

Myth no 6: High intensity exercise is the best way to lose weight.

Research shows that long duration, low impact exercise, such as walking or swimming, has a greater benefit on weight loss than short duration, high impact exercise, such as jogging or aerobics. A greater proportion of fat is used when the exercise intensity is low and when we are getting a good supply of oxygen. This means that even while we are exercising, we must continue to breathe easily and not puff and pant.

It's the lack of oxygen that causes an excess of lactic acid in the muscles and gives a burning sensation during high impact exercise. Lactic acid inhibits the mobilisation of fat as an energy source therefore if not enough oxygen is available or the intensity of exercise is too high, fat will not be used.

The Health Education Authority is now recommending 30 minutes of moderate exercise, like walking, five times a week. Previously it had recommended 20 minutes of high intensity exercise three times a week.

To make the walking a bit more taxing, you can put small weights on to your ankles which are attached by Velcro.

Research has found that the less muscle you have, the harder it is to lose weight, because muscle is metabolically active but body fat is inactive.

Therefore, when women diet, but don't exercise, 25 per cent of any weight lost is made up of water, muscle, bone and other lean tissue. Muscle mass uses up more calories than fat: up to 30 to 50 calories a day, compared with only 2 calories a day for fat.

Exercise physiologists have found that the best fat loss exercise programme is a combination of both cardiovascular and resistance training. Some studios have shown that over an eight week period, 30 minutes of exercise a day, split half and half between cardiovascular and resistance training, compared with 30 minutes of purely cardiovascular, gave an extra 3 kg (7 lbs) of fat loss. Research also shows that resistance training increases metabolism.

Resistance training includes lifting weights, callisthenics or using resistance machines in the gym. There are simple ways of doing this without the need for expensive equipment or even having to join a gym. You only need to invest in a set of dumbbells, which are available in varying weights; some people have used rice or sand filled bags to get a similar effect.

Start with the lowest weight dumbbell and increase over time as you become stronger. You do not need to lift enormous weights. The idea is simply to create a resistance against which your muscles have to work, thereby increasing muscle mass.


How much magnesium is good for the heart?

. . . or a rhinitis treatment free of eucalyptus?

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