In the world of health and wellness, weight control is one of the most important considerations. It is a key risk factor for many important medical conditions like diabetes, heart disease, stroke, and several cancers. It affects energy levels, mobility, and of course, self-esteem. It is also hugely challenging for many people – in today’s modern world the prevalence of overweight and obesity continues to climb despite the fact that most overweight people do want to be slimmer (for a mixture of reasons but usually a combination of appearance, energy, and health risk). This article will consider some of the most important terminology used in this field…
Body Mass Index (BMI). This is the most widely used measure of “weight”. It is a simple formula of weight in kilograms divided by height in metres, squared; or BMI = weight / (height x height). This essentially factors height into a person’s weight and therefore describes how “round” a person is. Because it uses simple measurements (we all know our height and weight) it is practical and easy to use individually and or in research or population studies. For these reasons it has become widely used. That being said it is not perfect, mainly because it does not account for body composition and so very muscular people may be classified as overweight or even obese when in truth, they are healthy – fortunately this really only applies to very muscular folks and for most of us, BMI is indeed a fair representation of our “weight for height”.
Underweight means a BMI of less than 18.5. This is usually the result of serious medical conditions like cancer of AIDS, or of some form of eating disorder or excessive dieting.
Healthy weight means a BMI between 18.5 and 25.0.
Overweight means a BMI between 25.1 and 30.0. This is associated with increased risk for several medical conditions.
Obese means a BMI greater than 30.0 and is associated with even greater increased health risk.
Energy balance refers to the main and most basic principle of weight control. Those who consume as much energy (in food) as they use (in activity and or exercise) will maintain their weight. Those who consume less than they use will lose weight. Those who consume more than they use will gain weight. There are complexities and subtleties and ongoing research, but it seems that this basic “arithmetic of weight control” holds true for all or at least the vast majority of us.
Energy, in the context of weight control, refers to the energy content of food. This is usually measured as calories or as kilojoules.
Macronutrients refers to the main categories of food, being protein, carbohydrate and fat. Many foods contain a combination of macronutrients, but we tend to classify foods based on the macronutrient they mostly contain (e.g. cheese offers protein and fat but is usually classed as a fat).
Protein is a macronutrient that contains amino acids, which are essential for a number of things, most notably building and maintaining muscle. Most balanced diets include a good ammount of lean (low fat) protein.
Carbohydrates are macronutrients that mainly provide energy. Carbs can be classified using glycaemic index (GI) where low GI carbs are slow-release and healthy and high GI carbs are fast release and less healthy. Sugar (as table sugar or in many processed foods and snacks) is a high-GI food and should be avoided or minimised by most of us whereas low GI carbs such as whole grain foods and most vegetables are healthier for most of us.
Fat is a macronutrient that contains a lot of energy but provides a number of essential nutrients such as Omega-3 fatty acids. A healthy diet should include a reasonable ammount of healthy fats such as fat from fishes (salmon, tuna, mackerel), nuts, and olives. There are many details and complexities here including saturated (unhealthy) vs unsaturated fats (better) and trans-fats (poisonous almost) etc but this is beyond the scope of this article really.
Micronutrients refers to trace elements like minerals and vitamins. These are essential for optimal health but do not contain any actual energy/calories and such play no or only a minor role in weight control. All of the three types of macronutrient (protein, carbohydrate, fat) contain various combinations of micronutrients.
Mediterranean diet is probably the most widely advocated eating plan today. It is based around lean protein (fish and nuts and legumes with limited meat and dairy), Low GI carbs (vegetables, whole grain breads, minimally processed foods) and healthy fats (unsaturated fats like olive oil, fish, nuts).
No-carb diets (e.g. Atkins, Paleo) restrict or exclude carbohydrate. These have helped some people to lose weight although most good research suggests that they are no more effective than a more balanced approach such as Mediterranean. In addition, there are some concerns around safety and sustainability.
Crash diets and severe restrictive diets do not work. They cannot be sustained over time and often lead to a yo-yo effect where any weight lost initially is regained rapidly. This effect ultimately creates a slower metabolism (food is metabolised more slowly and is more likely to be stored as body fat) and ever-increasing difficulty with weight control in the long term.
This list is by no means comprehensive, but a solid understanding of these terms should help you in your quest for a sustainable long term approach to the important matter of weight control.
Written by Dr Colin Burns
