Healthy eating habits/The Low Carbohydrate Diet: Curbing the Confusion

What is a Low Carbohydrate Diet?

Diets that replace carbohydrates with foods containing a higher percentage of fat or protein are referred to as Low-Carbohydrate Diets. An example of this is the Atkins diet. The Nutrient Reference Values adapted by the National Health and Medical Research Council recommend that carbohydrates should contribute between 45-65% of total energy for the day . Low carbohydrate diets reduce this to approximately 20% . The rationale behind the Low-Carbohydrate Diet is that once carbohydrate restriction has commenced and carbohydrate stores are exhausted, the body switches to fat metabolism to make energy. One of the products of fat metabolism is ketones, and an accumulation of ketones puts the body into a state of ketosis. This leads to a reduction in appetite and an overall effect of weight loss .

Risks of long-term low-carbohydrate dieting

Long-term carbohydrate restriction of between 20-60g/day can be detrimental to health . Risks include:

• A higher risk of heart disease due to a higher saturated fat intake .

• A 12% reduction in thyroid hormones. Thyroid hormones control metabolism. A reduced metabolism results in rapid weight re-gain once carbohydrates are re-introduced .

• Mood swings associated with a decreased availability of serotonin in the brain. Serotonin is responsible for elevating mood .

• Feelings of light-headedness, and decreased concentration due to low blood sugar levels .

• Bad breath due to ketone production .

• Vitamin, mineral (e.g. calcium and iron) and fibre deficiencies. This may lead to constipation, fatigue, headaches and other health outcomes .

Why do we need carbohydrates?

In order for the cells of the body to produce energy to sustain life, glucose is needed. The main source of glucose is carbohydrate foods (breads, cereals, rice). Fat and protein are much less efficient energy sources because they must firstly be broken down into their various components before they can enter the energy production pathway .

Carbohydrates are important for:

• Brain function. The brain requires 25% of the body’s glucose to function; therefore regular consumption of carbohydrates supports this and enables concentration to be maintained, which is important for studying .

• Fibre content. Low GI foods (e.g. wholemeal bread, brown rice, oats) are high in fibre and therefore prevent constipation .

• Weight stabilization. Low GI foods keep you feeling full for longer so appetite is regulated and snacking is reduced .

• Improving performance during exercise. Having a light carbohydrate-based snack before exercising (e.g. a piece of toast with jam) can improve performance because glucose is the number one fuel during exercise .

What types of carbohydrates should we eat?

There are two types of carbohydrates: simple, and complex.

Simple carbohydrates

Of the three types of simple carbohydrates, glucose is the most important. Both natural (fruits and vegetables) and processed foods (candy, chocolate, soft drink) contain simple sugars. Processed foods containing simple carbohydrates are referred to as ‘empty calories’ or ‘High GI foods’ because they provide a quick burst of energy without any nutritional benefit . The AGHE recommends consuming these foods in small quantities and infrequently .

Complex carbohydrates

Complex carbohydrates refer to unrefined/unprocessed wholegrain breads, cereals, as well as brown rice and quinoa that contain long chains of glucose molecules. They require more work by the body to digest. These are referred to as ‘Low GI foods’ because they provide a more sustained release of energy, keeping you fuller for longer as well as containing essential nutrients such as fibre, B group vitamins and folate . These types of carbohydrates should be selected.