Nutrition

In nutrition, the diet is the sum of food consumed by a person or other organism. Diet is critical to optimising human function, finely tuned, a good diet will increase energy, sense of well being and acumen. When properly composed the right diet can push every important quantifiable marker for health in the right direction. Dietary habits are the habitual decisions an individual or culture makes when choosing what foods to eat.  Individual dietary choices may be more or less healthy. Proper nutrition requires the proper ingestion and equally important, the absorption of vitamins, minerals, and fuel in the form of carbohydrates, proteins, and fats. Dietary habits and choices play a significant role in health and mortality

Carbohydrates:

Carbohydrates require less water to digest than proteins or fats and are the most common source of energy. Proteins and fat are vital building components for body tissue and cells and are also a source of energy for the body.

Carbohydrates are not essential nutrients: the body can obtain all its energy from protein and fats The brain cannot burn fat and needs glucose for energy, but the body can make this glucose from protein. Carbohydrates contain 3.75 and proteins 4 kilocalories per gram, respectively, while fats contain 9 kilocalories and alcohol contains 7 kilocalories per gram.

Foods that are high in carbohydrates include breads, pastas, beans, potatoes, bran, rice and cereals.

Protein:

Most microorganisms and plants can biosynthesize all 20 standard amino acids, while animals, (including humans) must obtain some of the amino acids from the diet. Key enzymes in the biosynthetic pathways that synthesize certain amino acids - such as aspartokinase, which catalyzes the first step in the synthesis of lysine, methionine, and threonine from aspartate - are not present in animals. The amino acids that an organism cannot synthesize on its own are referred to as essential amino acids. If amino acids are present in the environment, microorganisms can conserve energy by taking up the amino acids from their surroundings and downregulating their biosynthetic pathways.

In animals, amino acids are obtained through the consumption of foods containing protein. Ingested proteins are broken down through digestion, which typically involves denaturation of the protein through exposure to acid and hydrolysis by enzymes called proteases. Some ingested amino acids are used for protein biosynthesis, while others are converted to glucose through gluconeogenesis, or fed into the citric acid cycle. This use of protein as a fuel is particularly important under starvation conditions as it allows the body's own proteins to be used to support life, particularly those found in muscle.  Amino acids are also an important dietary source of nitrogen.

Fats:

Lipids play diverse and important roles in nutrition and health.Many lipids are absolutely essential for life. However, there is also considerable awareness that abnormal levels of certain lipids, particularly cholesterol (in hypercholesterolemia) and trans fatty acids, are risk factors for heart disease amongst others.

Humans have a requirement for certain essential fatty acids, such as linoleic acid (an omega-6 fatty acid) and alpha-linolenic acid (an omega-3 fatty acid) in the diet because they cannot be synthesized from simple precursors in the diet. Both of these fatty acids are 18-carbon polyunsaturated fatty acids differing in the number and position of the double bonds. Most vegetable oils are rich in linoleic acid (safflower, sunflower, and corn oils). Alpha-linolenic acid is found in the green leaves of plants, and in selected seeds, nuts and legumes (flax, canola, walnuts and soy). Fish oils are particularly rich in the longer-chain omega-6 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Most of the lipid found in food is in the form of triacylglycerols, cholesterol and phospholipids.

Most of the saturated fatty acids (as triacylglycerols) in the diet are incorporated into adipose tissue stores, because the absence of double bonds allows a higher energy yield per carbon than is obtained from oxidation of unsaturated fatty acids. The longer chain fatty acids are incorporated into cell membranes as phospholipids regardless of degree of saturation. Since dietary fatty acids are exchanged with membrane fatty acids, dietary fat composition is reflected in membrane lipid composition. Thus dietary fatty acids can influence cell function through effects on membrane properties. Dietary fat provides an average energy intake which is approximately twice that of carbohydrate or protein. A minimum amount of dietary fat is necessary to facilitate absorption of fat-soluble vitamins (A, D, E and K) and carotenoids. A minimal amount of body fat is also necessary to provide insulation that prevents heat loss and protects vital organs from shock due to ordinary activities.

So what should I eat?

I have been traning with CrossFit Sydney guys more than two years and they slowly put me on CrossFIt Diet. Now I have more physical and mental energy that ever.I can do workouts that I would have never dreamed of being able to do!

The CrossFit dietary prescription is as follows:
Protein should be lean and varied and account for about 30% of your total caloric load.
Carbohydrates should be predominantly low-glycemic and account for about 40% of your total caloric load.
Fat should be predominantly monounsaturated and account for about 30% of your total caloric load.
Calories should be set at between .7 and 1.0 grams of protein per pound of lean body mass depending on your activity level. The .7 figure is for moderate daily workout loads and the 1.0 figure is for the hardcore athlete.

In plain language, base your diet on garden vegetables, especially greens, lean meats, nuts and seeds, little starch, and no sugar. That's about as simple as we can get. Many have observed that keeping your grocery cart to the perimeter of the grocery store while avoiding the aisles is a great way to protect your health. Food is perishable. The stuff with long shelf life is all suspect. If you follow these simple guidelines you will benefit from nearly all that can be achieved through nutrition.

The Caveman or Paleolithic Model for Nutrition
Modern diets are ill suited for our genetic composition. Evolution has not kept pace with advances in agriculture and food processing resulting in a plague of health problems for modern man. Coronary heart disease, diabetes, cancer, osteoporosis, obesity and psychological dysfunction have all been scientifically linked to a diet too high in refined or processed carbohydrate. Search "Google" for Paleolithic nutrition, or diet. The return is extensive, compelling, and fascinating. The Caveman model is perfectly consistent with the CrossFit prescription.

Zone Diet

Are you confused in the abundance of diets that are "the best"? I was as well:-)
I'm trying to follow paleo/zone diet and it's working for me perfectly. I have to admit that it took me quite a while to get used to it (you might feel like a rabbit - eatieng vegies, vegies and for change green vegies, and necessary protein, ideally meat). I wasn't vegetarian but meat wasn't exactly my cup of tea, I could eat it once a week and that was it. I was training really hard, sometimes twice a day but I still had about 24% of body fat. Something was wrong. Typical diet of 60% carbohydrates 30% of protein and 10%fat was not giving me what my body needed. Zone diet recommends 40 % Carbs& 30% Protein & 30% Fats. Yeah, I know 30% of fats seems increadible but..........Eating fat does not make you fat. It's your body responce to excess carbohydrates in your diet that makes you fat. Your body has limited capacity to store excess carbodydrates but it can easily convert those excess carbohydrates into body fat.

The Paleo Diet

The Paleolithic Diet is based upon a simple theory - our genes determine our nutritional needs, and they developed in relation to the environment in which we evolved. For millions of years our hunter-gatherer ancestors ate combinations of lean meat, seafood, plants, fruit, and nuts. But today, more than 70% of our dietary calories come from foods that our Paleolithic (Stone Age) ancestors rarely if ever ate... and that modern humans are not genetically adapted to eat. These are the foods that are recommended to approximate a Paleo Diet.