Health news blog

Before you read any further, it’s important to appreciate the type of event where the G.I. factor will help. It is one in which the athlete is undertaking a very strenuous form of exercise for longer than 90 minutes. Exercise physiologists define this by saying that the athlete is exercising at more than 65 per cent of their maximum capacity for a prolonged period. Examples of such events include a running or swimming marathon, a triathlon, non-stop tennis competition or football game (depending on the player’s position). Some forms of recreation such as cross-country skiing and mountain climbing may also benefit from the G.I. approach. In some occupations that require prolonged strenuous activity for hours and hours (such as bush fire-fighting), low G.I. foods may be beneficial.

Low G.I. foods are best before an event—approximately two hours before the big race. The meal will have left the stomach by then but continues to be digested in the small intestine for hours afterwards. The slow rate of carbohydrate digestion in low G.I. foods helps ensure that a steady stream of glucose is released into the bloodstream during the event. The extra glucose is available when needed towards the end of the exercise when muscle carbohydrate stores are running low. In this way, low G.I. foods increase endurance and prolong the time before exhaustion hits.

It’s also important to select low G.I. foods that do not cause gastrointestinal discomfort such as stomach cramps and flatulence. Some low G.I. foods such as legumes are high in fibre or indigestible sugars. However, not all low G.I. foods are fibrous and high residue The high amylose rices (Basmati and Doongara) and any form of white pasta are good examples of low G.I. foods that don’t contain much fibre. Instant noodles have a low G.L, too. Athletes who are too nervous to eat a solid meal, may prefer a liquid supplement such as Sustagen™ sport, which has a low G.I. (43).

Helen O’Connor, a dietitian who works with many of Australia’s Olympic athletes, teaches them how to manipulate the G.I. factor of their diet. Her pocket guide The G.L factor and Sports Nutrition provides menu plans and case studies and more hints for eating and competing. Her book The Taste of Fitness is packed with low G.L recipes for sports people.

The food industry is keenly interested in the G.I. factor, too, and it won’t be long before there are specially formulated low G.I. foods on the supermarket shelves specifically aimed at the serious sports person. The sports drinks that are enjoying much popularity at present have a high G.L, between 70 and 80. So they may not be an advantage before the event, but they are an invaluable aid during the event when blood sugar needs to be topped up, as well as after the event when glycogen stores need to be replenished.

The following table shows the serving sizes of low G.I. foods containing 50 grams or 75 grams of carbohydrate.

You will not win if your pre-event meal is jiggling around in your stomach (this will affect the jogger more than the cyclist). So test the timing and amount of low G.I. food during your training sessions. Then you’ll be ready for the big day. Don’t try it out for the first time on the day of the competition!

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Male and female fat distribution and fat cell reactivity differs. Male-type centrally stored fat cells (around the abdomen) are known to be different in size and function to gluteal tissue, being more responsive to lipolytic and less responsive to lipogenic stimuli. Males generally use more energy for a set amount of exercise because of the larger proportion of lean body mass, or muscle, for a given body mass. Gluteal fat stores in females are widely regarded as having a biological function as an energy reserve for reproduction and milk production during lactation, and these are relatively resistant to fat loss even with high energy output or low energy intake.

Women experience greater hormonal swings throughout life (menarche, menstrual cycle, pregnancy and menopause) and these can impact significantly on body fat levels. The hormone levels in men by contrast, change only gradually with time as testosterone levels gradually decline with age. Women who don’t gain excessive weight during pregnancy, and who remain active both during pregnancy and after parturition, don’t seem to be at risk for extra fat gain—at least for the first 1-2 pregnancies. Women who are overfat or obese and who gain excessive weight during pregnancy are more likely to have problems after delivery. Breast-feeding mothers (over 6 months of breast-feeding) have been shown to stay leaner for longer than non-breast feeding mothers. In general also, the more babies a woman has, the greater her chances of becoming overfat or obese. It’s not known, however, whether this is due to physiological factors or the reduced ability to exercise and increased opportunity for over-eating, or whether it’s simply an association with other socioeconomic factors. Large families and obesity are more common in lower socioeconomic groups and the social status may be the determining factor for both.

Body composition differences between the genders also favour males in terms of energy expenditure. Men, in general, have a higher lean body mass to total mass ratio, with 12-24 per cent of body composition in the form of adipose tissue. Females on the other hand carry 15-30 per cent of their body mass in the form of fat. Higher lean body mass, even given constant weight, ensures a higher resting metabolic rate and hence men tend to have a greater energy use at rest. During exercise it has been shown that a man utilises up to 40 per cent more energy walking a set distance than a similar sized female.

Finally, there are psychological and sociological differences between the sexes which, although potentially changeable, can have a profound impact on body fat levels. The idealised female shape, for example, is now one of thinness. This has changed throughout history, there being good evidence (in art and literature) that a more ample female form has been preferred in the past. When fatness indicated wealth, a well-fed female body was desired. In the 20th century in Western countries, where energy-rich food is generally plentiful, fatness is easy and leanness is more associated with wealth, status and influence. Anorexia nervosa is the pathological extreme of this obsession with a thin figure.

Dietitian Jenny O’Dea from Sydney University has shown that females generally idealise a much thinner body size for themselves than is preferred by most males. The social pressures to conform to an ideal shape is greater in females (even if it is largely females who apply that pressure). A pot belly in a male doesn’t attract the same social pressures as a similar degree of fatness in a female, even though the male’s fatness is more dangerous to health.

Sex differences in body fatness have very real implications for fat loss planning. It is totally unrealistic to expect similar results from a male and female placed on the same type of fat loss program, although this is often expected by partners who may undertake the same kind of program. To the extreme frustration (and often guilt and depression) of the female partner, it is usually the male who is able to lose fat more easily and faster, and to keep this off longer, than the female. More support is often needed for females to ensure adequate eating patterns to encourage satisfaction with a body shape which is less than ideal and to prevent discouragement with slow fat losses.

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The energy content of foods, or the energy requirements of physical activities, can be measured in a number of ways. Basically there are three categories of measures that are used:

1. Direct calorimetry. Direct calorimetry can also be used to measure energy expenditure in the form of heat loss from the human body. This requires placing a person in a small chamber in which all the heat released is measured. Unfortunately, such chambers are very expensive and are only present in well-established research laboratories. Direct calorimetry can also be used to measure the energy content of food through ‘bomb calorimetry’, as previously discussed.

2. Indirect calorimetry. This calculates energy use directly from measurements of the amount of oxygen (O2) consumed, carbon dioxide (CO2) and nitrogen produced (the latter to eliminate protein metabolism in the equation). This can also be done in a chamber (metabolic or respiratory chamber) over periods of 24 hours or more, or it can be done with a hood system over a period of minutes or hours.

From indirect calorimetry equations, the amount of each type of energy substrate being used can also be calculated. This is expressed as the respiratory exchange ratio (RER), or respiratory quotient (RQ).

The RER, which is based on the ratio of oxygen (02) consumed to carbon dioxide (CO2) produced, can provide information about whether the predominant energy source being used is carbohydrate or fat. The theory behind this is that more oxygen is required to bum fat relative to the amount of carbon dioxide produced. In fact, the ratio of 02 to C02 is around 0.7 when fat is the total fuel being oxidised. On the other hand, when carbohydrate is used as a fuel, equal amounts of 02 and C02 are involved. Where carbohydrate is the sole fuel therefore the ratio of 02 to C02 is 1.0.

At rest, the terms respiratory exchange ratio (RER) and respiratory quotient (RQ) can be used interchangeably, although strictly speaking there is a difference. RER refers to the exchange ratio of gases expired, whereas RQ is a measure of the ratio of fuel use at the tissue level. RER, which is more relevant for our purposes here, is derived from the chemical calculations.

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Every baby, infant and child will experience various disorders of the abdomen and gastro-intestinal system. This is inevitable. The ones we have already discussed are among the more common. However, there is a huge list of others. The average child will not be involved in these, but without doubt a certain number of little ones are destined to contract one of them. Diagnosis is often difficult, and even doctors expert in the field of baby care may be hoodwinked and find the exact diagnosis takes time and many tests.

Only a few of the important but less common abdominal disorders are described on the following pages. It is not an exhaustive list of complaints, nor does it give more than brief general information. But it may offer some extra detail if a parent hears of the complaint or wishes to have some added knowledge.

As I have emphasized earlier, this book is intended to be used only as a general guide. It is not a do-it-yourself compendium, and is not intended to be used that way. Whilst many simple ailments may be treated at home by parents, others require proper medical diagnosis and supervision in treatment. Never begrudge money or time spent in having the best possible attention for your child. It may pay handsome dividends and may be life-saving.

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Sandwiches often form the basis of school lunches. It is far better to use whole-wheat or multi-grain bread or milk bread, rather than simple white or brown varieties. (Milk bread has a higher protein component, as protein from milk has been added.)

The fillings should be given careful thought. It is easy to make or marr the value of the sandwich with the contents. High-protein fillings include meat, cheese, and egg. Many ‘health food’ products are now commercially available, such as nut-meat and similar lines which are high in protein. Most of these contain gluten, the protein fraction of wheat. They can be used directly, or in conjunction with other items.

In fact, many sandwiches are far more appetising when they are combined with other products. For instance, any of the above protein items can readily and tastefully be included in a nice, thick, salad sandwich. Salad products give the sandwich a light, crunchy, attractive appearance and sensation when eating.

Use only a small amount of butter. Many mothers will use unsaturated margarine in preference. Adding a vitamin extract, such as Marmite, can upgrade the value of the sandwich.

Some mothers do away with bread altogether. This is replaced by a crisp salad. It is simple to prepare in a plastic, airtight dish and convey to school where it is eaten at the appropriate time.

Rather than include cakes and sweet biscuits, a packet of nuts, raisins, dried apricots (or peach or apple) and sultanas is far better. It is easy to make up a different pack each day—this can contain any one or a combination of the items suggested. Other items can be included that are of nutritional value.

A piece of fruit each day is also a good idea. It is wise to alternate these from day to day if possible, For example, have an orange one day, an apple the next, apricot or peach the next. This will depend on availability and price, but variation will cover a wider range of vitamin requirements. And it will often be more economical than cake and biscuits, which have little nutritive value.

The lunch pack can be broken up into segments that may be used for play lunches and lunch itself. Either let the child decide what to eat and when, or do this by making individual servings. It is so simple to wrap some nuts and pieces of dried fruit and place this parcel on the top, for morning recess.

An easy-to-prepare lunch pack consists of a couple of slices of cheese together with a few short pieces of celery. Or some cheese and a slice of fresh pineapple. There are unlimited possibilities.

The simplest and best beverage is, of course, cold water. When some chipped ice is added, this is the most refreshing drink available. It is far more thirst-quenching on hot days than sugar-based aerated beverages which contain about 420 kJ (100 calories) per glass. The latter frequently increase the body’s heat factor, even though they might be served cold.

Orange and lemon drinks are excellent. But their value can often be destroyed by adding loads of sugar. Freshly squeezed orange juice with no sugar is an excellent, healthful and refreshing drink. It is also high in vitamin C which is essential for good health.

If you encourage your child to buy his or her food, or if it is more convenient, first discuss the basics of healthy eating. Recommend fruits, nuts and dried fruits in preference to sweets and lollies. Meat pies and pastry are nutritionally useless, so try to phase a child out of this unhealthy habit. It is far better never to let it start.

Spending a little time and thought can pay handsome dividends. Why not opt for the sensible way, and prepare your children’s lunches yourself. Enlist their assistance and you can readily teach them the basics of healthful living, and long term good health.

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