There are three main macro-nutrients that we need to consume as part of our daily diet; carbohydrates, proteins and fat. They all have different energy values, effects and requirements within our bodies. Proteins are made of building blocks called amino acids, some of which our bodies can manufacture (non-essential amino acids) and some that the body can't (essential amino acids). Proteins have been in the spot light the last few years, with many diets ramping up the protein intake and decreasing the carbohydrate intake for weight loss. Protein is responsible for rebuilding and repairing the tissues of our body, such as muscle, hair and nails. It also plays and important role in regulating body processes, such as transporting nutrients and resisting disease. Protein is known to contribute to the maintenance of muscle mass, as well as growth in muscle mass and so it is particularly important for anyone that is partaking in exercise, especially resistance training. But how much protein is needed in the average diet to fulfil all of these functions?
It is estimated that the average person requires approximately 1g of protein per kg of body weight.
More exercise = More protein to replace amino acids used during exercise.
1.2g per kg a day is required for 1-1.5 hours of exercise.
1.4g per kg a day is required for 2-4 hours of exercise.
1.7g per kg a day is required for extreme exercise lasting 5 hours or more.
We can store fat, and we have a small ability to store carbohydrate in our muscles and our liver, but we cannot store protein. If we do not replenish protein on a daily basis, we will lose it from some part of our body; any loss of protein can represent a loss of function. So it is important to get our daily requirements, especially when trying to build muscle. Now building muscle used to be something only men did. The ladies would hang out in the cardio section of the gym on the treadmill and the cross trainer and then men in the free weights. However, it is now becoming more understood how important lean mass (muscle) is in all of our bodies, in weight management and general health. Now, this brings us back to calories, our basal metabolic rate and our active metabolic rate. Your BMR is how much energy is expended when an individual is at rest, this is about 75% of your total energy expenditure. This is in part determined by your lean mass (muscle), the more muscle someone has the higher their BMR and the more calories are burned at rest. This is due to a process called thermogenesis, which is the production of heat. So muscles are great for weight loss, lets get weight lifting ladies. Long term, strength training can also reduce the chances of osteoporosis and reduce the likelihood of injury, so build those muscles ladies and maintain them for life.
Proteins are important but the latest diet fads seam to encourage an increase in protein at the expense of carbohydrates. Now its fair to say that high protein/low carbohydrate diets can lead to weight loss. This is because when we exercise we burn carbohydrates first, then fat and then finally protein. Remember we cannot store protein so when we break it down for energy our body starts to break down muscles and proteins that are functional in our bodies. This is why increasing levels of exercise requires increasing levels of protein in our diet to account for this. However, significantly reducing carbohydrates means our body goes straight to fat burn when we exercise. Our bodies need fat and wants to hold onto it and so will limit how much fat we burn for energy. This means when skipping the carb burn you go straight to fat burn but then get to protein burn a lot quicker, breaking down muscle and reducing your lean mass. This leaves your body in a cycle of reducing fat AND muscle when you exercise and as muscle weighs more than fat you see the scales drop significantly, but at a price. Long-term you do not benefit from that lean mass increasing your metabolic rate, protecting you from injury and building up your strength. You burn less calories at rest and you will put on weight very easily as soon as you eat normally again or reduce the exercise you are doing.
So can exercise and low carbohydrate diets really go together? Our muscle's primary source of fuel is glucose, derived from breaking down carbohydrates. When non glucose (fats and proteins) is turned into glucose to provide fuel to the muscles this is less efficient than glucose. The end result is increased muscle fatigue, decreased muscle power, which leads to poor athletic performance, as shown in low carbohydrate studies. So how do we manage this? The secret to losing fat without losing muscle starts with not being too aggressive or extreme with your reduction of carbohydrates. Exercising on days where muscles are getting adequate carbohydrates for fuel and taking days off from exercise when you are limiting your carbohydrate intake. Reducing carbohydrates at the end of the day, after you have completed your workout for the day can also help keep the balance.