Every couple of years, a new fad diet comes out that make people jump on board, usually promises fast results. Most of these diets tend to restrict a food group. In this article, we'll be talking about carbohydrate restriction. Carbohydrates (known as glucose found in the blood and glycogen found in the muscles and liver) have been known to be the body’s primary source of energy. However, with recent research, there have been new approaches to macronutrient ratios. A Registered Dietitian is the best source to approach any dietary plans, but of course it's important to educate yourself on the effects of carbs on the body. These recommendations should be adjusted based on individual goals, body weight, total calories needed, and training volume/intensity.
The United States Department of Agriculture and Institute of Medicine have set dietary guidelines in terms of marcronutrients. For the general population, the goal is to promote overall health and ward off chronic diseases such as diabetes, hypertension, and cardiovascular diseases. These guidelines recommend that at least half of the carbohydrates consumed should be from complex, whole grains and sufficient in fruits and vegetables. The protein sources should be lean and fat sources should be unsaturated fats. The macronutrients ratio should be 45-65% carbohydrates, 10-35% protein, and 20-35% fats.
As for athletes, The Academy of Nutrition and Dietetics and the International Society of Sports Nutrition have recommended carbohydrate intake at 5-10g/kg of bodyweight for athletes in general, protein intake of 1.2-1.4 g/kg of bodyweight for endurance athletes, and 1.2-1.7 g/kg of bodyweight for strength athletes. However, athletes involved in high-intensity training can consume protein amounts up to 2.0 g/kg of bodyweight. Fat intake is the same at 20-35% of total calories.
The Paleo Diet is known for cutting out grains, dairy, and legumes with a heavy emphasis on animal-based protein. You may have also heard of this as "The Cave Man Diet." It involves slightly higher protein and fat than is generally recommended a about 23% carbohydrates, 38% protein, and 39% fat. The diet promotes increased performance, energy levels and improved body composition. Research has provided us with some pros and cons of the effectiveness of the diet on our bodies.
As for positives, it cuts out all processed foods, refined sugars, and grains, encouraging to eat fresh, whole foods. It recognizes carbohydrates as a source of energy during training and events.
However, with everything comes a weakness. It cuts out an entire food group of grains and dairy. Because of this depletion, diets will be low in fiber and calcium. Since it promotes animal based protein, it can be higher in saturated fats leading to higher cholesterol levels. Also, if you think about it, if you maintaining a diet of grass-fed meats and organic fruits and veggies, it can be quite expensive. Lastly, there is not much research on how the diet can affect athletes specifically.
Ketogenic diets restrict carbohydrates to less than 10% of total calories. The idea behind this is that since the body relys primarily on carbs as a fuel source, it has to switch to fats to use as fuel during this deficit. The body is placed in a state of ketosis which ketones are used instead of glucose during activity. Glycogen stores are depleted when in ketosis. Again, research has provided us with some pros and cons of the effectiveness of the diet on our bodies.
Improvements in body weight, body composition, energy, and endurance are noted, however, if training intensity increases, the ketones may not be able to properly fuel the body. Adaptation to this can take as little as 2 weeks, however in some as long as a few months if not done properly. The keto diet is no practical for high intensity exercise as the body usually needs to tap into glycogen stores for quick energy where as it is slower than using from ketones. Most importantly, because of a high fat diet, lipid and triglyceride levels will spike, which is a factor leading to cardiac disease.
All diets have positives and negatives associated with them. Each person is unique in regards to their own needs and metabolism. Eating habits should be created per individual and not as a group. Of course, the best macro distribution ratios are the ones that can be sustained without hindering performance. When choosing a diet, choose one that suits you best.