When it comes to losing weight, it’s not just about the number of kilojoules you eat; what you eat is just as important.
The weight loss mantra has always been as simple as “eat less and exercise more”, but growing research shows this isn’t actually the case and the message should be changed to “eat less refined carbohydrates and more whole foods, while sitting less, moving more and moving often”. While it has long been thought that a kilojoule is just a kilojoule, we now know this isn’t the case with not all kilojoules being created equal. In other words, the 840kJ you eat from a small sugary muffin is not the same as the 840kJ you eat from hummus with carrot and celery sticks. Processed carbohydrates such as sugary foods, soft drinks, and white bread cause sharp spikes and falls in blood sugar levels, which lead to higher hunger levels and greater activation in parts of the brain that regulate cravings, reward and addictive behaviours. We then seek out foods that restore our blood sugar levels quickly and this sets up a cycle of overeating driven by high GI foods. So, it’s important to remember that healthy eating and weight loss isn’t only about how much we eat, but also what we eat.
Keeping the Weight Off
For anyone who has tried to lose weight, you’ll probably agree that the hardest part isn’t losing the weight itself; it’s keeping it off in the long-term. Sure once we’ve succeeded at our weight loss goals, we start to become a little bit more complacent with things, indulging a little bit more and skipping a few more training sessions. But this isn’t the only contributing factor to our weight regain. Our body’s natural response to losing weight is to reduce the rate at which we burn kilojoules, as well as promoting an increase in hunger. It turns out, what you eat can significantly affect your metabolic rate. According to research by the New Balance Foundation Obesity Prevention Centre at Boston Children’s hospital, a diet full of processed foods and high GI carbohydrates, will eventually lead to a slower metabolism.
After getting study participants to lose 10-15 per cent weight loss, researchers Cara Eddeling and colleagues studied three different isocaloric diets: a very low-carb diet (10% energy from carbohydrates, 60% from fat and 30% from protein; a mixed diet containing foods with a low-GI (40% from carbohydrates, 40% from fat and 20% from protein; and a low-fat diet with a mix of carbohydrates generally with a high GI (60% from carbohydrate, 40% from fat and 20% from protein) in random order, each for four weeks. In terms of metabolism, the researchers found a big difference between the number of kilojoules burnt each day. While on the very low-carb diet, patients burned over 1200kJ more each day during normal daily activities compared to the time spent on the low-fat diet. According to the researchers, this number of kilojoules is the same amount of energy used in an hour of moderate exercise.
However, despite showing the greatest improvements in metabolic rate, the researchers found two potentially harmful effects of the very low-carb diet. During the course of the four weeks, levels of the stress hormone cortisol were higher on the very low-carb diet compared to the low-GI, moderate carb diet. Higher cortisol levels may promote fat storage, insulin resistance and cardiovascular disease. An inflammatory marker called c-reactive protein also tended to be higher with the very low-carb diet, compared to the low-GI diet. As a result, the researchers concluded that the low-GI diet offered the best results for weight loss maintenance, while also reducing the risk of various chronic diseases. The low-fat diet (the diet eaten by many of us in a bid to lose weight) performed the worse in the study not only reducing metabolic rate, but also raising levels of leptin (hormone that regulates fat storage), increasing the risk of diabetes and metabolic syndrome.
What to Eat