Nutritionist and personal trainer Ginny McArthur looks at why carbohydrates have earned such a bad reputation
Fat used to be the dieter’s enemy, causing food manufacturers to replace fat with sugar in low-fat foods. The result? We kept getting bigger and now there has been a backlash against carbohydrates.
So what are the facts? Well, we need carbohydrates to function and they are the body’s preferred fuel for energy. Did you know that 20 per cent of your daily calorie requirement goes on running your brain, which functions best on carbohydrates (glucose).
Have you ever been on a high-protein, high-fat, and low-carb diet? Did you feel great for the first few days? Did you lose lots of weight? Then did you get a foggy brain and become a bit emotional? Did you start to binge and put all the weight back on again?
When you are carb-depleted you cannot think straight. I once cut down on carbs for a body building competition, I swear I was not safe to drive! I got palpitations, I nearly got a divorce and afterwards I practically inhaled any starchy foods I could lay my hands on.
I often see clients who overeat at night simply because they have not eaten enough carbohydrate during the day. Your brain knows when you are in deficit and will set you up with cravings to make sure you refuel. The problem lies in the amount of refined carbohydrate and sugar that we consume daily and how little we choose to exercise.
How much carbohydrate you need in a day depends upon your activity level, weight, age and gender. It could be 4g of carbohydrate per kg of body weight for a 60kg, 35-year-old woman exercising for less than four hours a week or 10-12g of carbohydrate per kg per day for the same woman when she is training for an ironman.
We are designed to eat whole and natural foods that release their sugars slowly. Our caveman digestive system can cope with grass seeds bashed with a stone, but bleached white flour? Not so much.
Processing foods does most of the work for your digestive tract, so processed grains release their sugars quickly. When sugars enter the blood stream quickly, your body reacts by releasing insulin from the pancreas. Insulin is a hormone that pushes glucose out of your blood stream and into your cells. Insulin is also your ‘fat storage hormone’ – when your blood insulin levels are high you will not burn fat as a fuel.
So the idea is to eat carbohydrates that release their sugars slowly, avoiding a blood sugar spike and giving you a slow and steady energy release. These are foods with a low glycaemic index. Low GI carbohydrates are broken down into glucose and absorbed from the gut into the blood stream slowly.
Conversely when you are exercising for more than 90 minutes you might require high GI foods. This is because your blood is being pumped into your working muscles and you need a quick and easily digested energy source. For example lollies, ripe bananas or a sports drink.