With so many extreme diets claiming that their macronutrient ratio is the optimal for weight loss, or the new ‘revolutionary’ findings to the macronutrient exclusion needed to rid obesity, it is not surprising that we want to know more about the roles they have in the body, and what our ideal requirements are for wellbeing.
Low fat diets and low carbohydrate diets are commonly followed for weight loss, but is it really that simple, to just cut out one macronutrient to lose weight or to reduce cholesterol, and is this good for us?
What are macronutrients?
Macronutrients are the nutrients that provide the body with energy and include carbohydrate, fat and protein. Alcohol also provides calories, though it is not considered to be a macronutrient as it is not required for health. Our bodies also require micronutrients, including vitamins and minerals, in small quantities.
Carbohydrate is the preferred source of energy as all cells in the body, especially the brain, can function well on glucose, which is the broken-down form of carbohydrate. Carbohydrates can also easily be stored as glycogen in muscles and liver for later use. Fibre-rich carbohydrate foods are also very important for a healthy, functioning digestive system and the bulk helps to remove waste from the body, regulate hormones and cholesterol excretion and prevent diseases such as diverticulitis and bowel cancer.
Fat has certainly had a bad rap in the past, however it is hugely important for many bodily functions. Fat is the most dense source of energy and is essential for growth and development and functionality of cell membranes, it aids in the absorption and storage of fat-soluble vitamins A, D, E and K, protects organs and body tissues by providing cushioning, supports immune function and also regulates inflammation.
Think of protein as the building blocks needed for the body. Protein is made up of amino acids, which are essential components of all cells; protein is therefore needed for growth and repair, especially for growing children. Protein is also required for making hormones, and is important for maintenance of muscle mass.
The ideal balance
It would be easy if we could recommend a typical ‘ideal ratio’ of carbohydrate, fat and protein; in reality, however, this ratio varies significantly depending on the individual. Requirements for dietary macronutrient intake are largely determined by age, body weight and stage of life (such as pregnancy), but requirements also depend on a number of factors such as activity and health. The state of growth or weight loss is also a determinant for requirements of the specific macronutrients – for example, a body builder aiming to increase muscle tissue versus a dieter losing weight.
Government guidelines recommend that adults consume approximately 50% of calories from carbohydrates, 15% protein and 35% fat (1). This balance may be fine for the majority of the population most of the time, but, depending on your personal needs, this may vary.
When exercising at high levels, such as endurance sports athletes, a higher amount of carbohydrate may be required from the diet. If, on the other hand, a sedentary person is trying to lose weight, they may benefit from a slightly lower carbohydrate intake.
In body builders, growing children and pregnant or breast-feeding women, there is a net accumulation of body protein, so protein requirement will be higher. For those who have experienced trauma, have infection, inflammatory disease or are recovering from malnutrition, a slightly higher protein intake is also required to aid in repair and growth. It is believed that low to moderate intensity endurance exercise does not affect the requirements of dietary protein. Well-trained athletes training at high frequency and high intensity appear to have an increase of dietary protein requirements (2).
Negative effects of extreme diets
Low carbohydrate diets
A low carbohydrate diet is actually one of the most effective ways of losing weight (3), however it does come with drawbacks. Firstly, maintaining a very low carbohydrate diet (below 30g carbohydrates per day) is quite difficult in the long term. As fibre is generally found in carbohydrate-rich foods such as fruit & vegetables and grains, a low carbohydrate diet is naturally quite low in fibre, which can lead to constipation and hormone imbalances (fibre helps the body to flush out excess hormones). A very low carbohydrate/relatively high fat diet can also place stress on the kidneys, which may not be used to dealing with such high levels of protein, and the resulting production of ketones also produces bad breath, another unwanted side effect from such a diet.
A strict low carbohydrate diet may not be the healthiest or most pleasant diet to follow; however, reducing intake of refined carbohydrates such as sugar and foods containing white flour, and keeping carbohydrate intake to around 30-40% of calorie intake may be suitable for individuals struggling to keep body weight down. A reasonably low carbohydrate diet may be considered healthy if plenty of fibre and fresh fruits & vegetables are consumed, however the long-term health effects are unknown.
Low fat diets
It is common for people to follow a low fat diet with the view that this is the easiest way to lose weight as fat contains a high amount of calories. In reality, low fat diets are not the most successful for weight loss (3) and they also have many negative effects on the body. As fat is so essential to health and is involved in many bodily processes, a lack of fat in the diet may lead to a deficiency of the essential fatty acids which can only be obtained from foods such as nuts and seeds. A diet low in fat also reduces the ability of fat-soluble vitamins, (vitamin A, D, E and K,) to be absorbed. These vitamins are especially important for immune, skin and bone health. Low fat eating habits may leave you feeling unsatisfied, prone to illness and may cause bones to become fragile and skin to become dry and dull.
If you are following a low fat diet to reduce cholesterol, think again. It is the balance of different types of fats which determines your cholesterol levels and, most importantly, cardiovascular health (4). Include plenty of those fats which are liquid at room temperature, such as olive oil and flaxseed oil, as these fats help to keep cell membranes nice and fluid, allowing proper transportation of nutrients. Fish also contains very important fatty acids (omega 3 EPA) which help to increase healthy cholesterol. Coconut oil also has a beneficial effect on HDL cholesterol levels (5). It is particularly important to include the essential fats during pregnancy for brain development of the foetus.
Food sources of macronutrients
In simplistic terms, foods are often considered as either a ‘protein’ food or a ‘carbohydrate’ food, but they are not practically made up of one macronutrient. Oats, for example, are seen as a carbohydrate food, although the actual macronutrient content of 100g oats is carbohydrate 66.3g, protein 16.9g and fat 6.9g (the remaining content is mostly water) (6). As macronutrients have different calorie content per weight, when calculating the percentage of calories for each macronutrient in oats, this works out at approximately 70% carbohydrates, 15% protein and 15% fat.
When considering how much of a particular macronutrient to eat, it is important also to consider the type of macronutrient. Refined sugar and starches found in grains for example are both carbohydrates, but they have very different nutritional values. Here are some healthy food choices for your macronutrient intake:
Whole grains such as spelt, oats, rye, brown rice, wheat, barley and amaranth, quinoa, fruits, vegetables, beans and lentils.
Oils such as olive oil, coconut oil and walnut oil; nuts, seeds, fish, seafood, meat.
Meat, fish, eggs, cheese, yoghurt, nuts, seeds, tempeh, beans and lentils.
An easy way to ensure that you have a healthy balance of macronutrients without counting calories, reading labels or weighing food, is to aim to have half of your plate filled with colourful vegetables (providing carbohydrates and fibre), a small fist size of whole grains or starchy vegetables such as brown rice or a sweet potato, and a fist size of protein-rich food such as meat or fish. Also don’t forget your healthy fats by adding cold oils to salads and nuts and seeds with breakfast or for snacks. If you are vegetarian, you may need to increase your intake of protein-rich foods such as eggs, cheese, beans and lentils.
1. Department of Health (1991) Dietary Reference Values for Food Energy and Nutrients in the United Kingdom. HMSO, London.
2. Phillips SM, Van Loon LJ. Dietary protein for athletes: from requirements to optimum adaptation. J Sports Sci, 2011, 29 (1): 29-38.
3. Bueno NB, de Melo IS, de Oliveira SL, da Rocha Ataide T. Very-low-carbohydrate ketogenic diet v. low-fat diet for long-term weight loss: a meta-analysis of randomised controlled trials. Br J Nutr, 2013, 110 (7): 1178-87.
4. Mozaffarian D, Micha R, Wallace S (2010) Effects on Coronary Heart Disease of Increasing Polyunsaturated Fat in Place of Saturated Fat: A Systematic Review and Meta-Analysis of Randomized Controlled Trials. PLoS Med 7 (3).
5. Feranil AB, Duazo PL, Kuzawa CW, Adair LS. Coconut oil predicts a beneficial lipid profile in pre-menopausal women in the Philippines. Asia Pac J Clin Nutr, 2011, 20 (2): 190–195
6. Nutrition facts oats (2014). URL: http://nutritiondata.self.com/facts/cereal-grains-and-pasta/5708/2