The reason ‘eating healthy’ is so hard has nothing to do with willpower
- June 27, 2021
Dietitian and researcher, Dr. Catherine Itsiopoulos reveals how evolution is responsible for our unhealthy cravings, and why you should consider the Mediterranean diet as a satisfying alternative.
‘Your brain is a pig: How evolution has primed us to gorge ourselves on fattening foods’; this is the title of an article published on Canadian news site CBC.ca. It was written by Professor Gordon Orians, a professor emeritus of evolutionary biology at the University of Washington in Seattle.
The pig statement may be alarming, but it really does help to explain why following a healthy eating pattern can be so difficult to sustain. It also explains how, despite good intentions, our brains will often guide us to make food choices that are high in energy (kilojoules), fat and sugar.
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Origins of our food cravings
As humans, we evolved under conditions of food scarcity where our principal occupation was finding and consuming enough energy to stay alive. We are genetically engineered to prefer or seek out high-fat foods because fats are more energy dense – fat contains three times more energy per gram compared to carbohydrate-rich foods.
Not only was food scarce, but it also required a lot of energy (exercise/effort) to obtain and prepare. A few indigenous populations such as Aboriginal Australians, indigenous Eskimo populations in Alaska and, today, tribes in Ooty, India, still live a traditional hunter-gatherer lifestyle. When they are in their natural environments, they do not experience heart disease and diabetes. However, when they migrate to cities and change their dietary habits to consume processed foods and become less active, they rapidly develop diabetes and heart disease and at a faster rate than the populations already living in these cities.
Benefits of a Mediterranean diet
A Mediterranean diet is not quite a hunter-gatherer way of eating, but it does have many of the qualities that would be experienced by traditional hunter-gatherers: home gardens, plenty of vegetables and leafy greens, nuts, dried fruits, game meats and foods that are much less processed and therefore take lots of effort to produce.
The beauty of the Mediterranean diet is, relative to the Western diet, when we eat this way, it keeps us fuller for longer. And this is attributed to the bulkiness of the diet, which contains a high quantity of plant foods, especially leafy vegetables that have a high-water content. Foods with a high-water content are bulky and have fewer kilojoules per 100 g than foods with low-water content. In addition, foods that are carbohydrate-rich have lower kilojoules, as carbohydrates have a 16 kj/gram energy content versus fats, which have a 37 kj/gram energy content.
Legumes, which are full of fibre, also have a lower calorie/kilojoule value per meal compared to a meal rich in animal proteins and fats. A dietary pattern that has lower energy density has less energy (or kilojoules) per gram of food eaten. There is a vast difference in energy density between a bulky Mediterranean meal compared to a highly processed meal.
The Mediterranean diet has similarities with the hunter-gatherer lifestyle. Image: iStock.Source:BodyAndSoul
Which meal is more filling?
Here are two examples of typical lunches,each provides around 2400kj (600 calories).
- 120g lamb
- 300g vegetables with extra-virgin olive oil
- 1 piece of fruit
(620 calories, 44g protein, 34g fat,21g carbs, 98mg sodium). Energy density =1.1 cals/g food
Meal A. Image: supplied.Source:BodyAndSoul
- 180g cheeseburger and small fries
- 175ml small fruit juice
(600 calories, 21g protein, 25g fat, 65g carbs,793mg sodium). Energy density =3.3 cals/g food
Meal B. Image: supplied.Source:BodyAndSoul
Meal A is more filling, and infinitely more nutritious. It contains three times more solid food weight than Meal B. Meal A is also higher in protein, fibre and healthy fats, which all take longer to digest.
Meal B, however, is higher in processed carbohydrates, low in fibre and moderately low in protein, which will digest much faster. After Meal B you are more likely to snack within a few hours, whereas Meal A will keep you full for hours and you are less likely to snack.
‘The Heart Health Guide’ by Catherine Itsiopoulos, published by Macmillan, RRP $34.99. Image: Rob Palmer. Source:BodyAndSoul
This is an edited extract from The Healthy Heart Guide, by Dr. Catherine Itsiopoulos.
Dr. Catherine Itsiopoulos is an accredited practising dietitian, senior academic, international leader and researcher in Dietetics (particularly of the Mediterranean diet), and author of ‘The Heart Health Guide‘.
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