Body weight is a determinant of blood pressure at all age; in fact:
it has been estimated that the risk of developing elevated blood pressure is two to six time higher in overweight than in normal-weight individuals;
there is a linear correlation between blood pressure and body weight or body mass index (BMI) (a BMI greater than 27, i.e. overweight or obesity, is correlated with increased blood pressure): even when dietary sodium intake is held constant, the correlation between change in weight and change in blood pressure is linear;
centripetal distribution of body fat (waist circumference greater than 34 inches in women and 39 inches in man), also associated with insulin resistance, is more important determinant of blood pressure elevation than that peripherally located in both man and women;
it has been shown that weight loss, both in hypertensive and normotensive individual, can reduce blood pressure and reductions occur before, and without, attainment of a desirable body weight.
In view of the difficulties of sustaining weight loss, efforts to prevent weight gain among those who have normal body weight are critically important.
How to calculate BMI
BMI is total body weight, expressed in kilograms [kg] or pounds [lb], divided by the height squared, expressed in meters or inches (in.).
It can be calculated using the following equations:
BMI = weight [kg]/height2 [m] or
BMI = (weight [lb.]/heigth2 [in.]) x 705
BMI is a good indication of body fat because most of the weight differential among adults is due to body fat; its major flaw is that some muscular individuals may be classified as obese even if they are not.
A healthy BMI is between 18 to 24,9.
Overweight is considered to be between 25 to 29,9.
Obesity is categorized by BMI according to three grades:
30 to 34,9 I grade obesity;
35 to 40 II grade obesity:
40 and above III grade obesity.
Physical activity, and blood pressure
Maintaining a high level of physical activity is a critical factor in sustaining weight loss.
In addition to the effect on body weight, activity and exercise in itself reduce the rise in blood pressure.
Physical activity produces a fall in systolic blood pressure and diastolic blood pressure; so, increasing physical activity of low to moderate intensity to 30 to 45 minutes 3-4 days/week up to 1 hour nearly every day, as recommended by World Health Organization, is important for the primary prevention of hypertension.
Less active persons are 30% to 50% more likely to develop hypertension than active ones.
Remember: a rolling stone gathers no moss!
Shils M.E., Olson J.A., Shike M., Ross A.C. “Modern nutrition in health and disease” 9th ed., by Lippincott, Williams & Wilkins, 1999
Writing Group of the PREMIER Collaborative Research Group. Effects of Comprehensive Lifestyle Modification on Blood Pressure Control: Main Results of the PREMIER Clinical Trial. JAMA 2003;289:2083-2093 [Abstract]
World Health Organization, International Society of Hypertension Writing Group. 2003 World Health Organization (WHO)/International Society of Hypertension (ISH) statement on management of hypertension. Guidelines and recommendations. J Hyperten 2003;21:1983-92 [Abstract]
So, the best strategy for losing body fat is not a drastic reduction in caloric intake, nor follow constrictive or “strange” diets, such as hcg diet plan, sacred heart diet, paleo diet, Master Cleanse diet (the diet that Beyonce did), etc., that require to eliminate or greatly reduce the intake of certain macronutrients, mostly carbohydrates.
Such conducts can be:
very stressful from psychological point of view;
not passable for long periods;
hazardous to health because of inevitable nutrient deficiencies.
Finally, they do not ensure that all the weight lost is only or almost only body fat and are often followed by substantial increases in body weight (weight cycling or yo-yo effect).
An excessive reduction of energy intake means eating very little and this determines the risk, high, not to take adequate amounts of the various essential nutrients, that is, what we can’t synthesize, such as vitamins, certain amino acids, some fatty acids and minerals, including e.g. calcium, essential for bone metabolism at every stage of life, or iron, used in many body functions as the transport of oxygen to the tissues. This results in a depression of metabolism and hence a reduction in energy expenditure.
Whether the reduction in energy intake is excessive, or even there are periods of fasting, it adds insult to injury because a proportion of free fatty mass will be lost. How?
Body fat, reduction in energy intake and role of carbohydrates
Glucose is the only energy source for red blood cells and some brain areas, while other brain areas can also derive energy from ketone bodies, which are a product of fatty acid metabolism.
At rest, brain extracts 10% of the glucose from the bloodstream, a significant amount, about 75 mg/min., considering that its weight is about 1.5 kg. To maintain a constant glycemia, and thus ensure a constant supply of glucose to tissues, we needs to take carbohydrates or alternatively amino acids, both easily obtained from foods.
In the case of a low or absent dietary intake of carbohydrates, whereas after about 18 hours liver glycogen, which releases glucose into circulation, depletes, body synthesizes de novo glucose from certain amino acids through a process called gluconeogenesis (actually this metabolic pathway is active even after a normal meal but increases its importance in fasting).
But what’s the main source of amino acids in the body when their dietary intake is low or absent? Endogenous proteins, and there is a hierarchy in their use that is before we consume the less important and only after the most important ones. For the first digestive enzymes, pepsin, chymotrypsin, elastase, carboxypeptidase and aminopeptidase (around 35-40 g) will be used; successively liver and pancreas slow down their synthesis activities for export proteins and unused amino acids are directed to gluconeogenesis. It’s clear that these are quite modest reserves of amino acids and it is the muscle that will undertake to provide the required amounts of amino acids that is proteolysis of muscleproteins begins.
Note: Anyway, there is no absolute sequentiality in the degradation of several proteins, there is instead a plot in which, proceeding, some ways lose their importance and others will buy. So, to maintain constant glycemia the protein component of muscle is reduced, including skeletal muscle that is a tissue that represents a fairly good portion of the value of the basal metabolism and that, with exercise, can significantly increase its energy consumption: thus essential for weight loss and subsequent maintenance. It is as if the engine capacity was reduced.
One thing which we don’t think about is that heart is a muscle that may be subject to the same processes seen for skeletal muscle.
Ultimately make glucose from proteins, also food-borne, is like heat up the fire-place burning the furniture of the eighteenth century, amino acids, having available firewood, dietary carbohydrates.
Therefore, an adequate intake of carbohydrates with diet prevents excessive loss of proteins, namely, there is a saving effect of proteins played by carbohydrates.
Mammals, and therefore humans, can’t synthesize glucose from fats.
The elimination or substantial reduction in carbohydrate intake in the diet results in an increased intake of proteins, fats and cholesterol because it will increase the intake of animal products, one of the main defects in hyperproteic diet.
In the body there are no amino acids reserves, thus they are metabolized and, as a byproduct of their use, ammonia is formed and it’ll be eliminated as toxic. For this reason high-protein diets imply an extra work for liver and kidneys and also for this they are not without potential health risks.
An increased fat intake often results into an increased intake of saturated and trans fats and cholesterol, with all the consequences this may have on cardiovascular health.
What has been said so far should not induce to take large amounts of carbohydrates; this class of macronutrients should represent 55-60% of daily calories, fats 25-30% (primarily extra-virgin olive oil) and the remainder proteins: thus a composition in macronutrient that refers to prudent diet or Mediterranean Diet.
Body fat and the entry in a phase of famine/disease
A excessive reduction in caloric intake is registered by our defense mechanisms as an “entry” in a phase of famine/disease.
The abundance of food is a feature of our time, at least in industrialized countries, while our body evolved over hundreds of thousands of years during which there was no current abundance: so it’s been programmed to try to overcome with minimal damage periods of famine. If caloric intake is drastically reduced it mimics a famine: what body does is to lower consumption, lower the basal metabolism, that is, consumes less and therefore also not eating much we will not get great results. It is as if a machine is lowered the displacement, it’ll consume less (our body burns less body fat).
In summary, the best way to lose body fat, that also protects against future increases, is to make negative the daily caloric balance increasing physical activity and controlling food intake, i.e. change your own lifestyle.
Cereda E., Malavazos A.E., Caccialanza R., Rondanelli M., Fatati G. and Barichella M. Weight cycling is associated with body weight excess and abdominal fat accumulation: a cross-sectional study. Clin Nutr 2011;30(6):718-23. doi:https://doi.org/10.1016/j.clnu.2011.06.009
Giampietro M. L’alimentazione per l’esercizio fisico e lo sport. Il Pensiero Scientifico Editore. Prima edizione 2005
Ravussin E., Lillioja S., Knowler W.C., Christin L., Freymond D., Abbott W.G.H., Boyce V., Howard B.V., and Bogardus C. Reduced rate of energy expenditure as a risk factor for body-weight gain. N Engl J Med 1988;318:467-72.doi:10.1056/NEJM198802253180802
Sachiko T. St. Jeor S.T. St., Howard B.V., Prewitt T.E., Bovee V., Bazzarre T., Eckel T.H., for the AHA Nutrition Committee. Dietary Protein and Weight Reduction. A Statement for Healthcare Professionals From the Nutrition Committee of the Council on Nutrition, Physical Activity, and Metabolism of the American Heart Association. Circulation 2001;104:1869-74. doi:https://doi.org/10.1161/hc4001.096152
It is now accepted by athletes, coaches and athletic trainers that proper diet is one of the cornerstones for achieving better athletic performance. Despite this widely spread assumption, many, even at the highest levels, still believe that an high protein intake is fundamental in the athlete’s diet. This opinion is not new and is deeply rooted in the imaginary of many people almost as if, eating meat, even of big and strong animals, we were able to gain their strength and vitality too.
The function of proteins as energy-supplier for working muscle was hypothesized for the first time by von Liebig in ‘800 and it is because of his studies if, even today, animal proteins, and therefore meats, are often believed having great importance in the energy balance in the athlete’s diet, despite nearly two centuries in which biochemistry and sports medicine have made enormous progress.
Really, by the end of ‘800 von Pettenkofer and Voit and, at the beginning of ‘900, Christensen and Hansen retrenched their importance for energy purposes, also for the muscle engaged in sport performance, instead bringing out the prominent role played by carbohydrates and lipids.
Of course we shouldn’t think that proteins are not useful for the athlete or sedentary people. The question we need to answer is how many proteins a competitive athlete, engaged in intense and daily workouts, often two daily sessions (for 3-6 hours), 7/7, for more than 10 months a year, needs per day. We can immediately say that, compared to the general population, and with the exception of some sports, (see below) the recommended amount of protein is greater.
Metabolic fate of proteins at rest and during exercise
In a healthy adult subject engaged in a non-competitive physical activity, the daily protein requirements is about 0.85 g/kg desirable body weight, as shown by WHO.
Proteins turnover in healthy adults, about 3-4 g/kg body weight/day (or 210-280 g for a 70 kg adult), is slower for the muscle than the other tissues and decreasing with age, and is related to the amount of amino acids in the diet and protein catabolism. At rest the anabolic process, especially of synthesis, uses about 75% amino acids while the remaining 25% undergoes oxidative process, that will lead to CO2 and urea release (for the removal of ammonia). During physical activity, as result of the decreased availability of sugars, i.e. muscle glycogen and blood glucose used for energy purposes, as well as the intervention of cortisol, the percentage of amino acids destinated to anabolic processes is reduced while it increases that of amino acids diverted to catabolic processes, that is, it occurs an increase in the destruction of tissue proteins. At the end of physical activity, for about two hours, anabolic processes remain low whereupon it occurs their sharp increase that brings them to values higher than basal ones, so, training induces an increase in protein synthesis even in the absence of an increase in proteins intake.
What determines the daily protein requirements?
There are many factors to be taken into account in the calculation of the daily protein requirements.
The age of the subject (if, for example, he/she is in the age of development).
Gender: female athletes may require higher levels as their energy intake is lower.
An adequate carbohydrate intake reduces their consumption.
During physical activity, glucogenic amino acids may be used as energy source directly in the muscle, after their conversion to glucose in the liver through gluconeogenesis.
An adequate carbohydrate intake before and during prolonged exercise lowers the use of body proteins.
The energy intake of the diet.
A reduced energy intake increases protein requirements; conversely, the higher energy intake, the lower the amount of protein required to achieve nitrogen balance; usually there is a nitrogen retention of 1-2 mg per kcal introduced.
If the athlete is engaged in very hard competition/workouts, or if he requires an increase in muscle masses (e.g. strength sports) nitrogen balance must be positive; a negative balance indicates a loss of muscle mass.
The nitrogen balance is calculated as difference between the nitrogen taken with proteins (equal to: g. proteins/6.25) and the lost one (equal to: urinary urea in 24 hours, in g., x0.56]; in formula:
Nb (nitrogen balance) = (g. protein/6.25) – [urinary urea in 24 hours, in g., x0.56)]
The type of competition/workouts that the athlete is doing, either resistance or endurance, as well as the duration and intensity of the exercise itself.
Resistance training leads to an increase in protein turnover in muscle, stimulating protein synthesis to a greater extent than protein degradation; both processes are influenced by the recovery between a training and the next one as well as by the degree of training (more training less loss).
In the resistance and endurance performances the optimal protein requirements in younger people as for those who train less time are estimated at 1.3 to 1.5 g protein/kg body weight, while in adult athletes who train more time is slightly lower, about 1-1.2 g/Kg of body weight.
In subjects engaged in a hard physical activity, proteins are used not only for plastic purposes, which are incremented, but also for energy purposes being able to satisfy in some cases up to 10-15% of the total energy demand.
Indeed, intense aerobic performances, longer than 60 minutes, obtain about 3-5% of the consumed energy by the oxidation of protein substrates; if we add to this the proteins required for the repair of damaged tissue protein structures, it results a daily protein demand about 1.2 to 1.4 g/kg body weight.
If the effort is intense and longer than 90 minutes (as it may occur in road cycling, running, swimming, or cross-country skiing), also in relation to the amount of available glycogen in muscle and liver (see above), the amount of proteins used for energy purposes can get to satisfy, in the latter stages of a prolonged endurance exercise, 15% of the energy needs of the athlete.
The physical condition.
When needed, the desired weight.
Athletes attempting to lose weight or maintain a low weight may need more proteins.
From the above, protein requirements don’t exceed 1.5 g/kg body weight, also for an adult athlete engaged in intense and protracted workouts, while if you consider the amount of protein used for energy purposes, you do not go over 15% of the daily energy needs.
So, it’s clear that diets which supply higher amounts (sometimes much higher) of proteins aren’t of any use, stimulate the loss of calcium in bones and overload of work liver and kidney. Moreover, excess proteins don’t accumulate but are used to fat synthesis.
How to meet the increased protein requirements of athletes
A diet that provides 12 to 15% of its calories from protein will be quite sufficient to satisfy the needs of almost all of the athletes, also those engaged in exhausting workouts.
In fact, with the exception of some sports whose energy expenditure is low, close to that of sedentary subject (for example: shooting, or artistic and rhythmic gymnastics), athletes need a high amount of calories and, for some sports such as road cycling, swimming or cross-country skiing, it may be double/triple than that of a sedentary subject.
The increase in food intake is accompanied by a parallel increase in protein intake, because only a few foods such as honey, maltodextrin, fructose, sugar and vegetable oils are protein-free, or nearly protein-free.
Calculation of protein requirements of athletes
If you consider an energy demand of 3500 kcal/die, with a protein intake equal to 15% of total daily calories, you have:
3500 x 0.15 = 525 Kcal
As 1 gram of protein contains 4 calories, you obtain:
525/4 = 131 g of proteins
Dividing the number found by the highest protein requirements seen above (1.5 g/kg body weight/day), you obtain:
131/1.5 = 87 kg
that is, the energy needs of a 87 kg athlete engaged in intense workouts are satisfied.
Repeating the same calculations for a caloric intake of 5000 , you obtain 187 g of protein; dividing it by 1.5 the result is 125 kg, that is, the energy needs of a 125 kg athlete are satisfied.
These protein intakes can be met by a Mediterranean-type diet, without protein or amino acids supplements.
Giampietro M. L’alimentazione per l’esercizio fisico e lo sport. Il Pensiero Scientifico Editore. Prima edizione 2005
Protein and amino acid requirements in human nutrition. Report of a joint FAO/WHO/UNU expert consultation. 2002 (WHO technical report series ; no. 935) [PDF]
In order to maintain body weight: adjust caloric intake according to consumption
In order to maintain your body weight, energy intake with foods must match your individual needs, depending on age, sex and level of physical activity; calories exceeding needs accumulate in form of fat that will deposit in various parts of the body (typically in men, as in postmenopausal women, the accumulation area for excellence is abdomen).
An example: let’s assume an energy requirement of 2000 kcal with an intake of 2100 kcal. The extra 100 kcal could result from 30 g of pasta or 35 g of bread or a 25 g package of crackers or 120 g of potatoes or 10 g of oils from any source etc., not a particularly large amount of food. This modest calories surplus, if performed daily for one year leads us to take:
100 kcal x 365 days = 36500 kcal/year extra calories compared to needs.
Since a kilogram of body fat contains approximately 7000 kcal, if we assume that 36500 kcal in excess accumulate exclusively in form of fat (very plausible approximation), we obtain: 36500/7000 = about 5 kilogram of body fat.
So, even a modest daily calorie surplus, over a year, can lead to a substantial body weight gain in the form of fat mass.
This example shows the importance of estimating with accuracy our daily energy requirements.
In order to maintain body weight: split daily caloric intake into multiple meals
Let’s assume that daily caloric requirement to maintain body weight is equal to 2000 kcal.
Is it the same thing if they are consumed in just two meals, maybe dividing them in half between lunch and dinner, or is it advisable to take three to five meals during a day?
In order to mantain body weight, the best choice is to divide calories into five meals: breakfast, lunch and dinner, the most abundant, plus two snacks, one on mid-morning and the other on mid-afternoon. Why? There are various reasons.
Consuming only two meals during the day, lunch and dinner or breakfast and dinner, it is likely to approach both meals with a hunger difficult to control; we eat what we have on our plate already thinking about what else to eat, having the feeling of not being able to satisfy the hunger. We eat, but there is always room for more food. Among the reasons for this there are too many hours between meals. Two examples:
dinner at 8:00 p.m. and, the next day, lunch at 1:00 p.m.: the interval is 17 hours, more than 2/3 of a day;
breakfast at 7:00 a.m. and dinner to 8:00 p.m., 13 hours have passed, most of which are spent in working activities and therefore more energy-consuming than hours of sleep.
Then, drops in blood sugar levels (glycemia) can also occur: liver glycogen stores, essential for maintaining normal glycemia, with time intervals between meals previously seen, can easily reach values close to depletion.
Therefore, by splitting the daily caloric intake into two meals, it is most likely difficult to meet the target of assuming 2000 kcal (the suggested daily calorie intake).
The concentration of too many calories in a single meal may promote the increase of plasma triglycerides, the excess of which is linked to the onset of cardiovascular disease.
When accumulating almost all or all of the calories in just two meals we are likely to grow stout, have feelings of bloating and getting real digestive problems due to excess of ingested food, not to mention that could occur even a postprandial sleepiness or difficulties in getting asleep.
In order to maintain body weight: exercise regularly
Physical activity has a central role both in maintaining the reached body weight and in the loss of fat mass.
Make physical activity on a regular basis has several advantages.
If exercise is conducted on a regular basis and is structured in the proper way, is possible that, even without appreciable changes in weight, a redistribution of fat occurs between fat mass, which drops, and free fat mass, which, on the contrary, increases. Such a result can’t obviously be reached by simple walk; we need a specific training program, better if planned by a professional, and a proper diet, always of Mediterranean type.
We protect muscle mass (and as suggested in point 1. we can also increase it).
We maintain a high metabolism.
Muscle burn energy during and especially after exercise.
The body is toned.
Appetite is controlled more easily.
Making physical activity on a regular basis makes the prevention of weight gain easier, due to the inevitable “escapades” (indulging in a bit of chocolate, an ice cream etc..).
Giampietro M. L’alimentazione per l’esercizio fisico e lo sport. Il Pensiero Scientifico Editore. Prima edizione 2005
Shils M.E., Olson J.A., Shike M., Ross A.C.: “Modern nutrition in health and disease” 9th ed. 1999
Biochemistry and Nutrition