Certain foods are extremely difficult for the human body to convert into body fat - not impossible but damned near impossible. By consuming calories derived from these foods, the anabolic margin of error is extended dramatically, which means it will be easier to lose fat and gain muscle, if you choose.
Lean protein, protein devoid of saturated fat, has been the staple, the bedrock nutrient of elite athletes for 50 years. Why? You can eat a mountain of lean protein and not get fat - assuming you train with intensity sufficient enough to trigger muscle growth. Lean protein is difficult for the body to break down and digest. As a direct result of this digestive difficulty, the body kicks the metabolic thermostat upward to break protein down into subcomponent amino acids.
The human body wants to preserve stored body fat as a last line of defense against starvation. If overworked and under-fed, the body will preferentially eat muscle tissue to save precious body fat.
Obese people that go on crash diets, precipitously slashing calories, might lose 100-pounds of body weight, yet still appear fat. Despite losing from say 350-pounds to 250-pounds, they still appear fat because they still are fat. The body has cannibalized muscle tissue and saved the fat. Though they might weigh 100-pounds less, they still possess 25-40% body fat percentile.
Lean protein is the bedrock nutrient in the physical renovation process because it supplies muscle tissue battered by a high intensity weight workout with the amino acids needed to heal, recover and construct new muscle tissue. Lean protein is a bedrock nutrient in the physical renovation process because it causes the basal metabolic rate (BMR) to elevate; the metabolic thermostat, the rate at which our body consumes calories, increases when digesting protein. Lean protein is a bedrock nutrient in the physical renovation process because it is damned near impossible for the body to convert it into body fat.
The other bedrock nutrient in the physical transformation process is fibrous carbohydrates: carrots, broccoli, green beans, bell peppers, spinach, cauliflower, onions, asparagus, cabbage, salad greens, Brussels sprouts and the like. Fibrous carbohydrates, like lean protein, are nearly impossible for the body to convert into body fat. Fibrous carbohydrates require almost as many calories to digest as they contain. A green bean or carrot might contain 10-calories yet is so dense and difficult to break down that the body has to expend nearly as many calories to break down that bean or carrot as the vegetable contains.
Fibrous carbohydrates have a wonderful "Roto-Rooter" effect on the internal plumbing: as they work their way though the digestive passageways they scrape mucus and gunk off intestinal walls and help keep sludge buildup to a minimum. For this reason fibrous carbohydrates are the perfect compliment to a lean protein diet. Too much protein can cause bile buildup: fiber is the Yin to protein's Yang. The two nutrients should be eaten together.
Both protein and fiber have a beneficial dampening effect on insulin secretions. It is no accident that professional bodybuilders, the world's best dieters, capable of reducing body fat percentiles to 5% while maintaining incredible muscle mass, construct their eating regimen around protein and fiber.
The best way to eat is to eat often. If you eat 3,000 calories a day the best way is in five 600-calorie feeding or six 500-calorie feedings instead of a breakfast containing 400-calories, a lunch of 1000-calories and a late dinner of 1,600-calories. Avoid calories easily converted into body fat.
Eat multiple small meals in the 400-600 calorie range comprised exclusively of foods near impossible for the body to convert into body fat. Plus, these foods cause the metabolism, the BMR, the body thermostat to elevate in order to digest them. Optimally you should eat every three hours: in about the time the nutrients from the previous meal have dwindled, been expended and exhausted, in about the time the elevated metabolism is 'settling back down to normal,' eat another small protein/fiber meal. This reestablishes anabolism, kicks the metabolism upward once again and gives the body more practice at assimilating and distributing quality nutrients.
They say practice makes perfect and by eating small, power-packed, tough to digest meals every three hours, the metabolism is kept elevated, anabolism is established and maintained and the individual never feels hungry. A person who is not hungry is far less inclined to binge on sweets and treats, junk and trash then the crash diet/calorie cutters who always feel hungry, deprived, listless and lacking energy.
The small meal/protein/fiber approach has been used successfully by elite athletes for decades and is not some untried dietary abstraction - rather it is the proven method of choice, one that has withstood the test of time, one that has been used for decades and been proven effective time after time.
If a person is able to establish a multiple meal schedule comprised primarily of lean protein and fiber eaten every three hours, then adds to this eating schedule some serious weight training and a cardiovascular regimen, physical transformation is a biological certainty.