Practical session 2 - Group 2

BODY COMPOSITION WORKSHOP

Obesity is a public health problem due to its impact on morbidity and mortality, the reduction of quality of life and the health care costs. Data from the ENRICA study published in 2012 indicate that the prevalence of obesity in the adult population in Spain is 22.9% (24.4% in men and 21.4% in women). According to the World Health Organization (WHO), in 2008 approximately 1.5 billion of adults (ages 20 or +) worldwide were overweight with 500 million of them being obese:

An accurate and precise classification of overweight and obesity is required, since the consequences of overweight and obesity are more than mere aesthetic problems due to their high impact on health. Normal weight, overweight and obesity can be defined by the body mass index (BMI) and by the percentage of body fat.

Body mass index

Obesity is defined as an excess of adiposity that presents a risk to health. BMI is used in the clinical practice to evaluate the ponderal categories of the patients. The BMI (kg/m2) is calculated as a person's weight (kg) divided by the square of his/her height in metres (m). The WHO Expert Committee proposed the following BMI cutoff values for the classification of adult ponderal categories:

BMI is the most frequently used diagnostic tool for the classification of obesity, because it is an easy and reproducible measurement. In spite of its wide use for the assessment of overweight and obesity, BMI is not an accurate measurement of body fat; for example, individuals of high muscle mass will exhibit higher BMI and older adults will tend to have more body fat than younger adults for a same BMI due to skeletal muscle mass loss.

Body fat percentage

Overweight and obesity can be also assessed by using the percentage of body fat (i.e. total fat mass divided by total body mass). There is a sexual dimorphism in the percentage of body fat, with women generally having a higher percentage of body fat than men because of gender-specific fat depots in mammary glands and the gluteo-femoral region. A healthy range of body fat for women is 20-30%, whereas for men it is 10-20%. Gender-specific cutoff points for the classification of ponderal categories according to the percentage of body fat are shown below:

Practical exercise

Mary is a 25-year-old woman that practices sport daily with a BMI=26 kg/m2 and a percentage of body fat of 21%, and John is a 31-year-old man that works in an office, with a sedentary life and a BMI=26 kg/m2 and a percentage of body fat of 26%. What is their ponderal category?












Response: According to their BMI, Mary and John should be classified as overweight; however, according to their percentage of body fat (a better surrogate measurement of adiposity), Mary would be classified as normal weight, whereas John would be classified as obese. 

1. You will need to know the cutoff values for the classification of an individual as normal weight, overweight or obese according to the BMI and the percentage of body fat. There are gender-specific differences for the percentage of body fat due to the higher accumulation of fat in the mammary glands and gluteo-femoral region in women.
2. Several methods for the evaluation of body composition can be used, such as plicometry, electric bioimpedance, hydrodensitometry, air displacement plethysmography (Bod-Pod), dual energy X-ray absorptiometry (DEXA), magnetic resonance imaging and echography, among others.
3. Visceral or android obesity is associated with higher cardiovascular risk, metabolic alterations and an increase in morbi-mortality compared with subcutaneous or gynoid obesity. An easy way for the evaluation of visceral obesity in the clinical practice is the measurement of the waist circumference (cm) or the waist-to-hip ratio (WHR). You will need to know the gender-specific cutoff points of waist circumference and WHR associated with increased and substantially increased cardiometabolic risk.

PHYSICAL ACTIVITY WORKSHOP

Physical activity is defined as any body movement produced by skeletal muscles that requires energy expenditure. Although physical inactivity has been identified as the fourth risk factor for global mortality, increasing levels of physical inactivity are seen worldwide. Furthermore, sedentarism is estimated to be an important cause for the development of different types of cancers, diabetes and cardiovascular diseases. In this sense, regular and adequate levels of physical activity help to maintain a healthy body as well as to be more likely to maintain its weight.

The term physical activity should not be mistaken with exercise. Exercise is a subcategory of physical activity that is planned, structured and repetitive. Physical activity includes sports, exercise and other activities such as playing, walking, gardening, briskly pushing a baby stroller, climbing the stairs, and dancing.

 

There are some types of physical activity especially beneficial: 

1. Aerobic activities make your heart beat faster. Aerobic activities can be moderate or vigorous in their intensity.
2. Muscle-strengthening activities make your muscles stronger. These include activities like push-ups and lifting weights.
3. Bone-strengthening activities promotes bone growth and strength. These activities, like jumping, are especially important for children.
4. Balance and stretching activities enhance physical stability and flexibility. Examples are dancing, yoga or martial arts.

1. Total energy expenditure is the energy required by the organism daily and it is determined by the sum of several components: basal metabolism rate, diet-induced thermogenesis and physical activity, among others.

 

2. Physical activity represents the thermic effect of any body movement produced by skeletal muscles that requires energy expenditure. A great variability inter- and intra-individual is shown. In active individuals, the energy required for physical activity corresponds to one to two times that of the basal energy expenditure while in sedentary individuals it can represent less than half.

3. Sedentarism or physical inactivity comes up as the disease of the modern society, being identified as the fourth leading risk factor for global mortality. Sedentarism substantially increases the probability of developing obesity, cardiovascular diseases, diabetes or certain cancers.

4. Sedentarism has been positively correlated with chronic low-grade inflammation associated with obesity.

5. Different dimensions are used to describe physical activity:

• Frequency: sessions or days per week.
• Intensity: amount of effort required for the activity: low, moderate or vigorous.
• Duration: length of session or accumulated length of physical activity during a week.
• Type: other info about the nature of the activity.

6. American Heart Association recommendations for healthy adults aged 18 to 65 years:

• At least 30 minutes of moderate-intensity aerobic activity at least 5 days per week for a total of 150 minutes

      OR

• At least 25 minutes of vigorous aerobic activity at least 3 days per week for a total of 75 minutes; or a combination of the two

      AND

• Moderate to high intensity muscle-strengthening activity at least 2 or more days per week for additional health benefits.

7. The Metabolic Equivalent of Task (MET) corresponds to a physiological measure expressing the energy cost of physical activities. MET is defined as the amount of oxygen consumed while sitting at rest and is equal to 3,5 ml O2 per kg body weight per minute.

8. Two principal methods of assessing physical activity levels are described:

• Subjective methods, depending on our own perception. They are predominantly used for measurements in populations, e.g., questionnaires of physical activity, diaries, logs or recall surveys.

• The objective methods often rely on solid data or observations. These methods are predominantly used for measurements in individuals, e.g., pedometers, heart-rate telemeters, accelerometers, electronic motion sensors, calorimetry, doubly labelled water as well as direct observation.

What do the sedentarism and hibernation have in common?

Basal metabolic rate consists in the amount of energy expended daily by humans and other animals at rest. It corresponds to the minimal quantity of energy required to maintain vital physiological functions such as corporal temperature, respiration, circulation or the functioning of different organs such as liver, kidneys or brain.

Basal metabolic rate is lower in sedentary lifestyle people compared to that of active individuals. In the same way, under hibernation conditions metabolic activity declines precipitously to roughly 5% of the non-hibernating basal metabolic rate.