When is a Calorie Not a Calorie
It is important to be aware of the calories in food when it comes to assisting your weight loss efforts.
The ‘Golden Rule’ when it comes to weight loss is: ‘Calories (energy) In’ must be less than ‘Calories (energy) Out’. By doing so you create a calorie (energy) deficit in the body and can therefore lose weight.
However, the source of those calories can also have an impact on the type of body tissue you lose.
For example, let’s consider the impact the calories in food would have if you went on 3 different diets. Each of the diets puts a much greater emphasis on one macro nutrient (carbohydrate, protein and fat) compared to the other two.
Firstly, lets consider what would happen if you had most of your daily calories coming from carbohydrate and very little of them coming from protein or fat.
The emphasis on carbohydrate is going to have a massive impact on your blood glucose levels. Even if low GI foods are consumed, if most of your calories in food are coming from carbohydrates it will still result in massive fluctuations in your blood glucose level because of the amount consumed.
This would induce insulin secretion, which would then cause much of the carbohydrate to be stored in the body. Some would be stored as glycogen in the muscles and liver but once those two storage sites were full the rest would be stored as body fat.
Plus, the high level of insulin would stop the body from mobilizing and utilizing fat as a fuel source; fat burning would stop.
The low protein intake would mean that protein synthesis (tissue construction) would be affected. Since the body is a dynamic structure, meaning that it is constantly breakdown and building up body tissues, a lack of protein would cause more breaking down than building up to occur.
This would result in a loss of body tissue, particularly muscle, which causes a slowing of the metabolic rate (muscle is a very metabolically-active body tissue). This would make further weight loss more difficult.
If the calories in food were mainly from protein, the blood amino acid level would increase, which would induce secretion of glucagon (insulin’s counter-regulatory hormone). This would cause the mobilization of glucose from the glycogen (stored carbohydrate) in the liver, which would help to maintain the blood glucose level. The amino acids in the blood stream would also induce a small insulin secretion, which would tend to promote the uptake of the amino acids into body tissues. This may help to preserve the lean body tissues (including muscle), which would help to keep the metabolism elevated.
As a result, the weight that is lost would mainly come from stored carbohydrate, which means water would be lost as well. Plus, fat from the fat stores would also be lost because glucagon promotes fat mobilization in the body.
The problem with a very high protein intake is sustainability. It is very hard to stick to a high protein diet long term. Plus, nutrient deficiency is likely to occur due to a lack of fruits and vegetables (carbohydrates) in the diet. Also, most high protein-containing foods (animal products) come with a high level of fat, which may have an impact on general health.
If the calories in food were mainly from fat, the blood levels of fatty acids would increase. This would have no impact on the insulin/ glucagon axis but the high levels of free fatty acids would still cause fat storage in the body.
The low blood glucose and blood amino acids levels would mean a loss of glycogen (and water) in the body as well as a loss of lean tissue (muscle), which would have a negative impact on the body’s metabolism.
For best weight-loss results, the ideal macro nutrient profile would be one that emphasises slightly more protein, a little less carbohydrate and then even less fat. The macro nutrient profile would look something like this: 30-40% of calories from carbohydrate; 30-50% of calories from protein; 20-30% of calories from fat.