Proteins are the building blocks for your body. It allows the enzymes to work properly. Protein is also required to allow proper sleep at night because it controls the melatonin/tryptophan cycle for your circadian rhythms. Protein is responsible for all your DNA/RNA functioning. You can live without carbohydrates but not without fat and protein. This is demonstrated in the way that the Inuit or natives above the Arctic Circle survived in cold climates by eating meat and fat from seals, whales, and polar bear. The Inuit also ate the organ meats which was the primary source of their vitamins.
I do believe that lack of protein may be the reason that we are so fat. Carbohydrates give us energy and vitamins and minerals. However, large quantities of carbs will make you fat because of the high calorie content from sugar. Let's say you get up in the morning and eat what is commonly considered a healthy breakfast meal of cereal. A serving of Frosted Mini-Wheat's, 1.8 oz. serving (24 biscuits) has 180 calories, 4 grams (g) protein. In addition you have a cup of orange juice. This is about 111 calories with only 1.7g of protein. At lunch you have a Subway Chicken Teriyaki with spinach salad. This gives you 220 calories and 27 grams of protein. You have eaten well and only consumed 511 calories. For diner you decide to have steak with mash potatoes, a salad, and garlic bread. The six ounces of meat is about 42 grams of protein. With lean and fat that is 438 calories. The 1-1/2 cup of mash potatoes is about 305 calories and 5.7 grams of protein. You also have two slices of garlic bread for 412 calories and 9.8 grams of protein. The mixed green salad with tomatoes, cumber, onions, green pepper, and dressing is 171 calories and 2g protein.
You add up the total and you have had about 1800 calories or what you believe is just right for a 150 lb. forty year old person. This is enough for your BMR calorie requirement. Your activity requirement is 500 calories because you have a desk job or are otherwise sedentary. You make this up by having snacks throughout the day that are primarily carbs and adds only 6 grams of protein. You total up your protein to find that you have 98 grams. How much protein should you have? Most health sites list protein at least 1/2 gram per pound of body weight or 75 to 85 grams as a minimum requirement. You have accomplished a great day of nutrition by most standards. But who do you know that eats that healthy.
Another typical day and you have two pieces of wheat toast with jelly and a glass of orange juice. 350 calories and 2 grams of protein. You have a McDonald's Quarter Pound with cheese meal for lunch with a coke. 520 plus 29 grams protein, fries 230, 2 g protein, 16 oz. coke 140 calorie. For diner: 6 oz. chili beans with cheese for 740 calories and 24 grams of protein and corn chips 2 oz. for 280 calories and 4g protein. This gives you 2260 calories and 61 g of protein. You don't feel well. You did have an adequate amount of calories. You worked out extra hard at the gym to burn off the fat and sugar and your muscles are aching and yet you still feel hungry. Why? It would seem that you had enough protein since you ate meat and cheese at two meals. However, you did not get the minimum requirement of protein. If you eliminated the toast for breakfast and had ham and eggs without the bread, you would have done fine even with all the sugar consumption at lunch.
The total protein and fat requirement is more important than the amount of calories that you eat. The above example with adequate protein from a breakfast of ham and eggs would have allowed you to feel stronger during your workout and the recovery would have been quicker. Also, you most likely would have slept and felt well.
The minimum requirement of protein is extremely important to how you feel. Getting the correct amount of vitamins and minerals is also very important. I went for a year eating junk food to see what it did to my lipids. I did gain a significant amount of weight. I ignored the amount of fat that I ate. However, my lipids, cholesterol and triglycerides were all normal with adequate protein, vitamins, and minerals. This is amazing since before getting an adequate amount of protein, enough minerals and especially vitamin D3, I had cholesterol as high as 140 and my triglycerides were as high as 700. Do not attempt this!
To better understand the requirements of protein, I would suggest that you visit Krispin.com to determine your protein requirements. All about protein.