The macronutrients: Carbohydrate, protein and fat
Which
ones and how much??
1. THE PROTEIN TO CARBOHYDRATE
RATIO
There is currently a lot of debate regarding the ratio of
carbohydrate versus protein that should make up our diet, especially when we
are trying to lose weight (or gain muscle).
High protein diets are currently the “in thing” and everybody seems to
be trying to avoid the “dreaded carbohydrate”.
Here are some facts I have gathered that help justify why the plate
model (pictured in my previous post) - ¼
of your plate low GI carbohydrates, ¼ low saturated fat protein (animal and/or
plant sources) and ½ plate low-starch vegetables, is what I recommend to my
clients.
The basics
Energy
content of nutrients:
|
Nutrient
|
kJ/g
|
Kcal/g
|
|
Protein
|
16
|
4
|
|
CHO (Carbohydrate)
|
17
|
4
|
|
Alcohol
|
29
|
7
|
|
Fat
|
37
|
9
|
|
Water
|
-
|
-
|
|
Vitamins, trace elements
And minerals
|
-
|
-
|
So, one gram of fat
contains about twice the amount of calories as one gram of carbohydrate or
protein.
Also, note how high
the energy density of alcohol is!
Macronutrients are
broken down into energy in the following order:
1. Alcohol
2. Carbohydrate
and Protein
2. Fat
(note: in most
circumstances when alcohol has not been consumed, protein is immediately taken
up by muscles for repair and rebuilding , thus carbohydrate is the first energy
source to be used.)
Evidence supporting
increasing protein in the diet
A review of studies undertaken by
Halton & Hu (2004) in the Journal of the American College of Nutrition
found that convincing evidence is present to suggest that protein exerts an
increased thermic effect when compared to fat and carbohydrate. The thermic effect of a food is, in essence,
the amount of energy required for that food to be digested and absorbed, plus
the amount of energy required to dispose of its waste products. The thermic effect of protein is
approximately 20-35% of energy consumed, whereas the thermic effect of
carbohydrate and fat is only in the range of about 5-15%.
The same study examined the effect of
protein on satiety and subsequent energy intake. The available evidence suggested that protein
rich foods increase satiety and thus decrease subsequent energy intake, at
least in the short term, although it is difficult to separate these results
from the effects of palatability, food mass, energy density, fibre and
glycaemic index. (Halton & Hu, 2004)
Halton and Hu (2004) also noted that
the studied data suggested that exchanging refined carbohydrates for protein
improved blood lipid profiles, reduced blood pressure and reduced the risk of
coronary artery disease.
Higher
protein diets have also been associated increased lean muscle body composition
when consumed in association with exercise.
Having an adequate protein intake when on a calorie deficient diet is
essential to prevent muscle wasting.
Evidence against high
protein diets:
Increasing protein intake leads to a
greater production of nitrogen (waste product of protein digestion) and
therefore urea, increasing the load on the kidneys (nitrogen is excreted from
the body via the kidneys). In patients
with decreased kidney function, or at risk of decreased function, such as
diabetics, this can be potentially dangerous.
High protein diets also have the potential to increase the risk of gout,
due to higher levels of uric acid in the blood and to interfere with calcium
metabolism, increasing the risk of osteoporosis. (Nutrition Australia, 2006)
It is important to note that, as seen
in the above table, the energy density of protein is much the same as that of
carbohydrate. If protein intake is in
excess of that required for growth and repair by the body, it is simply broken
down and used for energy; or, if calories ingested is greater than calories
consumed, stored as fat.
Some people—such as body
builders and weight lifters—adopt high protein diets based on the theory that
muscle consists of protein, and that high protein intake will lead to greater
muscularity. This argument is analogous to the belief that if a little vitamin
A is good for you, a lot of vitamin A is even better. In fact, high doses of
vitamin A are toxic (for example, excessive vitamin A intake has led to deaths
in stranded Antarctic explorers who ate the livers of their husky dogs).
Similarly, protein intake
above about 1.5-1.7 grams per kilogram of body weight is not only pointless,
but potentially harmful. (Nutrition Australia)
Evidence for
restricting carbohydrate intake:
The rationale behind carbohydrate
restriction is that, in response to lower glucose availability, changes in
insulin and glucagon concentrations will direct the body away from fat storage
and toward fat oxidation. (Westman, et al., 2007)
Recent studies have shown that under
conditions of carbohydrate restriction, the body shifts from burning glucose
and fatty acids for energy to fatty acids (from dietary fat and adipose (fat)
stores) and ketones (from dietary fat, protein and adipose stores). Glucose dependent tissues (i.e. red blood
cells, retina, lens and renal medulla) receive glucose through gluconeogenesis
(glucose production at the liver) and glycogenolysis (release of glucose from
muscle glycogen). Even if no dietary
carbohydrate is consumed, it is estimated that 200 g/day of glucose and be
manufactured by the liver and kidney from dietary protein and fat. (Westman, et al., 2007)
Ad-libitum fed carbohydrate-restricted
diets have been shown to reduce appetite, facilitate weight loss and improve markers
of cardiovascular disease such as fasting triacylglycerols, HDL cholesterol and
the ratio of total HDL cholesterol. Low carbohydrate diets have been shown to
improve glycaemic control and insulin resistance in otherwise healthy people
with Type II diabetes. (Westman, et al., 2007) .
Whereas the loss of lean body mass is
typical with weight loss, under certain circumstances when sufficient dietary
protein is provided, a LCKD (low carbohydrate ketogenic diet) may preserve lean
body mass even during hypoenergetic conditions of weight loss (Westman, et al., 2007) .
The elimination or reduction of dietary carbohydrates removes many
processed foods from the diet. (Westman, et al., 2007)
Evidence against carbohydrate
restriction:
On a low carbohydrate diet, the body is
forced to use some of its glycogen (the form of carbohydrate that is stored in
the liver and muscles) to maintain a normal blood sugar level. Some water that was stored with the glycogen
is also released and excreted, adding to short-term “weight” loss, but note,
this is not FAT loss! (Nutrition Australia, 2006)
Many low carbohydrate diets that
restrict intake of plant foods such as certain fruits and vegetables are
unlikely to supply sufficient quantities of dietary fibre and some vitamins and
minerals. (Nutrition Australia,
2006) Plant foods also contain a myriad
of other chemicals (phytochemicals) whose value to health is not yet fully
understood, but restricting these foods could have more detriment to our health
than we already know. Evidence shows
that increased consumption of a wide range of plant-based food sources is
associated with improved health and increased life expectancy (Nutrition
Australia, 2006)
Due to the elimination of food groups
rich in essential vitamins and minerals, VLCKD require vitamin, mineral and
fibre supplementation in order to prevent deficiency symptoms and constipation. (Westman, et al., 2007) . Reported side effects include: constipation,
headache, muscle cramps, diarrhea, weakness and skin rash. (Westman, et al., 2007)
Carbohydrate is the most direct and
preferred source of glucose that not only powers our muscles, but also provides
fuel for our brain. This means that
high-protein, low carbohydrate diets have the potential to interfere with the
efficiency of both mental and physical work. (Nutrition Australia, 2006).
Studies on these diets have only been
carried out, to date, in the short-term and longer study durations are required
to determine adverse event profiles.
But what the evidence does
not take into account:
Despite the evidence for and against particular macronutrient
ratios, these studies all fail to take into account the psychosocial aspects of
diet and nutrition; that is, how we feel about food, how it tastes and the
other ways in which it is used in our lives, other than purely for an energy
source. I will not go into this in depth
at this time, but we all know that there is more to eating healthy than simply
knowing what to and not to eat and, as mentioned earlier, any diet that
restricts ANY food group has the potential not only to be unbalanced, leading
to deficiencies, but also to lead the dieter down the path of the binge-diet
cycle, ultimately resulting in GREATER weight GAIN!
IN ADDITION: I do not believe that one should have to consume
expensive vitamin or mineral supplements in order to fulfill their body’s
requirements while putting themselves through a restrictive diet purely to be
thin. Any diet that does not provide all
of the nutrients we require for our bodies to function efficiently IS NOT
balanced and should not be used for long-term health (unless under specific guidance
by a practitioner).
So, in summary, here is my recommendation of protein to carbohydrate
ratios:
Include protein at every meal, in order
to take advantage of the thermic effect of protein and its effect on
satiety. Choose lean (low saturated fat) proteins from both plant and animal sources. Choose protein instead of refined
carbohydrates (hi GI carbohydrates, such as sugar), but do not increase protein
intake to the detriment of low GI, nutrient rich fruit and vegetable intake.
Gram for gram, balance low-glycaemic
index carbohydrates with lean protein sources in roughly equal amounts, but, as
per the plate model, make up the majority (50%) of your plate with fresh, low
starch salads and vegetables.
NEXT: Proteins,
Carbohydrates and Fats, the good, the bad and the ugly.
Now that we know generally
what our plate should look like and why, we will go through what are the BEST
choices of foods to fit into these macronutrient categories.
References:
Halton,
T. L., & Hu, F. B. (2004). The Effects of High Protein Diets on
Thermogenesis, Satiety and Weight Loss: A Critical Review. Journal of the
Americal College of Nutrition , 23 (5), 373-385.
Nutrition
Australia. (2006). Nutrition Australia: Nutrition Fact Sheet. High Protein
Diets .
Westman,
E. C., Feinman, R. D., Mavropoulos, J. C., Vernon, M. C., Volek, J. S.,
Wortman, J. A., et al. (2007). Low-Carbohydrate Nutrition and Metabolism. Americal
Journal of Clinical Nutrition , 86, 276-84.
