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Latest News - Edition
3
LATEST NEWS will provide you with information
and handy hints for maintaining a healthy lifestyle.
LOW
CARBOHYDRATE VS. HIGH CARBOHYDRATE DIETS: Whats the Story?
Maintaining a healthy body weight is a constant
struggle for many individuals and the incidence of obesity
is increasing at a staggering rate. In an attempt to lose
weight, many individuals move from one 'fad' diet to another,
each promising significant weight loss in a minimal amount
of time. Dieting is considered a short term solution to a
problem that is often made worse by this type of 'yo-yo' eating
pattern.
The latest trend in weight loss techniques is a low carbohydrate,
high protein way of eating, as embraced by many high profile
individuals and celebrities. Low-CHO diets do result in significant
short-term weight loss but most of this is not body fat and
weight loss is not maintained long-term. There are a number
of health risks associated with prolonged high protein diets
and low-CHO diets are not be the answer for continued weight
loss and optimal health into the future. Unfortunately most
people are after a quick fix and are not prepared to make
the long-term changes required for sustained successful body
fat loss.
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WHAT
CAUSES RAPID WEIGHT LOSS IN FIRST WEEK OF LOW CARBOHYDRATE
DIETS
Low-carbohydrate diets generally result
in weight loss of several kilograms in the initial one to
two weeks. Australians tend to have an addiction to bathroom
scales, however weight on the scales is not a true indication
of body fat loss and changes in body composition. Science
assures us that carbohydrate is rarely converted to fat in
the body, but is stored in the muscles and liver as glycogen.
Each gram of carbohydrate is stored with around 3-4g water.
The body can store about 500g carbohydrate with 1500-2000g
water, a total 2-2.5kg in weight. As carbohydrate storage
is reduced through reduced food intake, we lose carbohydrate
from the body plus the associated stored water. The initial
dramatic weight loss following reduction in carbohydrate intake
is predominantly water, not body fat. The focus for health
should be on reducing body fat levels rather than concentrating
on weight.
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ENERGY
BALANCE
Think about the typical Australian diet.
Cereal or toast for breakfast, a sandwich for lunch, pasta
or stir fry with rice or noodles, snacks of muesli bars, chocolate,
fruit and savoury crisps/snacks. Our diet is generally high
in carbohydrate, and often consists of high-glycaemic index
carbohydrates which can enhance feelings of hunger and lead
to overeating.
When an individual starts a low-carbohydrate diet, they are
invariably reducing the total volume of food consumed and
therefore total calories consumed. If total calorie intake
is reduced to below individual requirements, weight loss will
occur:
ENERGY INTAKE > ENERGY EXPENDITURE = BODY FAT GAIN
Many people consume far more calories from carbohydrates than
their body requires. If calorie intake is reduced to below
energy requirements, body fat loss will result, whether the
calories are from carbohydrate, protein, fat or alcohol.
Low-fat diets are often promoted for optimal weight loss.
Fat has double the amount of calories compared to carbohydrate
and protein, therefore a reduction in fat intake is a priority
for reducing total calorie intake. A mistake that many people
make is replacing fat with carbohydrates, often in unlimited
and excessive volumes. When carbohydrates are eaten in excess
they are not converted to fat as is often reported.
Excess carbohydrate in the body is preferentially broken down
by the body for fuel, often in place of fat which may otherwise
have been broken down. Excessive intake of calories, regardless
of source, will prevent body fat break down and result in
weight gain. A reduction in carbohydrate intake or total calorie
intake may be warranted in many situations, however severe
restriction of carbohydrate has a number of negative consequences.
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NEGATIVE ASPECTS OF LOW-CARBOHYDRATE
DIETS
LOSS OF MUSCLE
MASS
In addition to losing body water, low-carbohydrate
diets also lead to loss of muscle mass. Our brain, heart and
muscle use glucose as the preferential fuel source. When levels
are low and there is no continual supply to the blood, the
body must produce its own glucose. Fat can be broken down
to produce glucose, however this is a slow process and the
body can breakdown proteins more rapidly to maintain blood
glucose levels. Muscle burns fat, therefore hen muscle is
broken down the capacity to burn fat (both during exercise
and at rest) is reduced. In other words, low-carbohydrate
diets can reduce metabolic rate and the rate we burn fat.
Recent research shows that habitual high carbohydrate intake
may result in >10% higher resting basal metabolic rate than
low carbohydrate diet, as the body has to work harder and
expend more energy to digest carbohydrate (particularly high
fibre foods) than protein or fat. Protein will cause a smaller
increase in metabolic rate, with fat the most easily absorbed
and digested and a large proportion going straight to body
fat stores.
REGULATION OF OXIDATION
Unlike carbohydrates, protein consumed in excess of requirements
is not stored in the body and is either broken down or can
be converted to fat. Carbohydrates are unlikely to be converted
to fat and our bodies are able to increase oxidation rate
when we overeat high carbohydrate foods. This mechanism is
not as well regulated for protein and we are unable to regulate
fat oxidation.
FATIGUE
Chronic low blood glucose levels lead to mental and physical
fatigue. Breakdown of protein in the body also leads to the
production of ketone bodies, which decrease blood pH and can
lead to fatigue and illness.
Low energy levels experienced from low carbohydrate diets
effect the ability to sustain this type of eating plan long
term, particularly for active people. Some people indicate
improvements in energy levels in the early stages of low carbohydrate
diets but this is often due to initial weight loss and lighter
foods in the stomach, and improvements are generally not sustained.
SUSTAINABILITY
Continuation of high protein diets long-term is often impaired
by limitations in food choices and variety. Low-carbohydrate
eating centres on foods such as eggs, meat, chicken, fish,
nuts, natural yoghurt, 'watery' vegetables and tofu. Limited
food choice can lead to binges and can precipitate negative
eating patterns.
HEALTH RISKS
By-products of protein
breakdown must be excreted by the kidneys and there is speculation
as to long-term effects on kidneys and risk of kidney disease.
Foods that are rich in protein can also be high in fat. Animal
foods such as meat and dairy foods contain saturated fat and
this can contribute to risk of dangerously high blood cholesterol
levels and heart disease.
Cutting out food groups, such as breads, cereals, fruit, some
vegetables and dairy foods, can lead to inadequate intake
of certain nutrients, which can lead to fatigue and increased
risk of illness. Fibre is the major nutrient of concern, with
the possibility of increased risk of heart disease, diabetes,
cancer and obesity with low intake.
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HOW
DO CARBOHYDRATES EFFECT INSULIN LEVELS
Supporters of low carbohydrate diets argue
that carbohydrate intake stimulates the body's insulin response.
Insulin is a hormone produced by the pancreas that allows
glucose to enter body cells and also plays a role in body
fat storage. It is claimed that high intake of carbohydrate
will stimulate insulin release and cause weight gain as body
fat. Current medical research illustrates that the insulin
response is different according to type of carbohydrate consumed
- some foods effect blood glucose and insulin levels more
than others.
Foods containing carbohydrate have been scientifically tested
and rated according to blood glucose response (glycaemic index
of foods). Many common foods that are high in carbohydrate
are slowly absorbed by the body and do not cause rapid increases
in blood glucose and insulin levels (low glycaemic index).
By incorporating more low glycaemic index choices, carbohydrate
foods can be incorporated into the diet without significantly
increasing blood insulin levels. Recent research has indicated
that high protein foods may in fact produce a greater insulin
response than low-glycaemic index foods such as white pasta!
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EFFECTS OF SATIETY
Low-glycaemic index
carbohydrates are important for preventing hunger and sugar
cravings, due to effects on blood sugar levels. Including
some protein in meals and snacks can further enhance this
effect.
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CONCLUSION
Low carbohydrate diets are becoming
increasingly popular but are difficult to maintain long-term
and may have negative health effects. The reduction in metabolic
rate with prolonged low-carbohydrate, high protein intake
is likely to result in body fat gain in excess of initial
'pre-diet' levels when the regime is ceased. Scientific evidence
continues to indicate that a high carbohydrate (preferably
low glycaemic index), low fat, moderate protein diet is the
most effective for long-term control of body fat levels. A
healthy body composition is achieved by sensible balanced
eating and regular exercise, which also provides the added
benefits of optimal health, improved energy and reduced stress
levels.
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PAST
LATEST NEWS
Lisa Middleton,
Sports Dietitian & Fitness Consultant
Website: www.lisamiddleton.com.au
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