CALORIE CONTENT OF MACRONUTRIENTS
Calories and macronutrients are not independent variables in nutrition. Calories, as described in the last chapter, are units of energy. All the macronutrients supply energy and, therefore, contain calories. The per gram calorie content of each macro is:
•Protein: 4 calories per gram
•Carbohydrate: 4 calories per gram
•Fat: 9 calories per gram
As you can see, while both protein and carbohydrate carry only 4 calories per gram of macronutrient, fats have more than double, with 9 calories per gram of fat. This information will play a role in your diet construction and in how you allocate amounts of macronutrients to fit within your calorie constraints.
The Caloric Constraint Hypothesis
Since we cannot consume macronutrients without their inherent calorie content, and since calorie considerations are first priority in diet design, all three macros must be manipulated in concert to fit pre-made calorie restrictions or demands. This idea is termed the Caloric Constraint Hypothesis (CCH). Since your dietary goal will begin with a total calorie count, this total will dictate how macronutrients can be distributed within your diet. When one macronutrient amount is raised or lowered, either one or both of the remaining macronutrients must be adjusted as well to keep calories constant. Since all of the macronutrients have an effect on diet outcomes, it would be incorrect to simply say “eat more protein to grow muscle” without considering what the effect will be on carbohydrate and fat intakes. Thus, in assigning macronutrient totals, you should determine the total calories needed for the goal, determine optimal ranges of macronutrient totals, and then adjust those macronutrients to both meet minimum values and fit within the caloric constraints. There may be a few possibilities within the constraints and macro ranges where trade-offs can be made for desired outcomes or preferences. In chapter 10 we will go into exactly how to make the decisions and calculations for macronutrient ratios within a caloric constraint.
Figure 3.1. A depicts protein, carb, and fat ratios when protein is set at its optimum. B, C, and D illustrate the relative carb and fat deficiencies that can result from overeating protein within a given caloric constraint.
PROTEIN
Protein is made of large molecules which are made of other, smaller molecules called amino acids. Protein makes up many of the tissues in the human body and comprises enzymes that govern reactions and underlie most bodily functions at some level. Human proteins are comprised of 20 amino acids, of which our bodies can produce 11 endogenously. The other nine amino acids must be ingested via food sources.
There is a balance between protein degradation and protein synthesis in the body, termed “protein turnover.” Some of the amino acids that are liberated when protein is degraded are lost in urine, sweat, and other bodily fluids. Cells full of protein are lost constantly in skin, hair, and intestinal lining. Other amino acids are burned for energy, especially when carbohydrates and fats are not available in sufficient quantities to meet immediate energy demand. In order to address this net loss, amino acids must be consumed regularly via protein consumption.
Protein is critical to survival and health, but it also plays an important role in performance and body composition. Muscle mass is predominantly constructed from protein. Actin, myosin, titin, nebulin, and many other protein compose the contractile apparatus. Protein from the diet supports replenishment of skeletal muscle as it is broken down to support important bodily functions–this helps keep your muscles from shrinking over time. Thus, protein consumption is anti-catabolic as it helps maintain muscle tissue equilibrium. When muscle growth is the goal, there must be a positive net balance of amino acids. Building new tissue is termed “anabolism.” Constructing new muscle with an amino acid surplus is an example of an anabolic process.
In terms of performance, enzymes (made of protein), mediate all energy-liberating and movement-producing activity in the human body. Protein also makes up a huge percentage of connective tissues such as tendons, ligaments, and bones. Undereating protein not only shrinks the muscles that drive performance, but it can also reduce the amount of hemoglobin (the unit that helps blood carry oxygen to the muscles) that supports endurance, weaken joints and bones, and degrade functions supporting health–the base upon which performance is built.
Figure 3.2 Protein has the largest impact on body composition and performance of the macronutrients and thus must be a priority in a structured diet.
Because amino acids literally are the building blocks of most of our body’s functional and structural machinery and because new amino acids are mostly sourced from diet, protein is the most important macronutrient for body composition and health. Research on performance and body composition shows that although variations in fat and carb intake significantly impact outcomes, variation in protein availability also does so to a much greater extent.
Minimum, Maximum, and Recommended Daily Protein Intake
We have two means of establishing maximum protein intake. The first is to ask whether some amount of dietary protein can be toxic. Protein needs to be broken down into the constituent molecules, and many of the by-products are processed by the kidneys. Though an important consideration, both theoretical supposition (what volumes of protein breakdown would be required to overtax the kidneys) and direct evidence from carefully controlled research point to the same conclusion: There appears to be no realistic protein amount that is dangerous for human consumption (this, of course, excludes individuals with kidney disease or other conditions requiring restricted protein intake). Recent research tested outcomes of up to 2.0 g per pound of bodyweight per day and found no ill health effects. This amount is probably more than most people would realistically eat on any diet that accounted for macronutrients anyway, so not the most useful figure in determining protein maxima.
The second means of establishing a top end for protein intake comes from caloric constraint and the need for minimum intake of other macronutrients. It is from the CCH that a more applicable maximum protein amount comes. Very simply, if you eat all your daily calories in protein, you will not be able to get sufficient fats or carbohydrates, and your health, sport performance, and recovery will suffer. Maximum protein intake is as much protein as can be eaten within the caloric constraint while still allowing the minimum amounts of fat and carbohydrate for health.
Somewhere between this and the minimum protein needed lies an optimal range of intakes. It would be great if we could recommend one minimum protein intake amount that would fit all dietary needs. Unfortunately, the minimum protein to support health differs from the minimum amount of protein needed to gain muscle and so on. In order to calculate the appropriate range, assessing protein minima for various purposes (health and various specific sports) is required.
Protein Needs for General Health
The minimum amount of daily protein needed for health is about 0.3 g of protein per pound of bodyweight. Note that this minimum is not a recommendation for physique or performance, it is the minimum needed just for health.
Current research cannot agree on a specific value of protein intake for best health. Some studies have suggested that better health comes from a lower protein diet, but these conclusions were probably not the best interpretation of the data. When variables such as saturated fat intake or overly processed food consumption are accounted for in literature reviews, it appears that individuals who eat mostly whole food diets that include high protein are just as healthy as their low-protein counterparts (and likely have better physiques). It does seem that the consumption