Exercise and obesity

Edited by Dr. Stefano Casali

»Dynamics of adipose tissue

At six months of age it constitutes 25% of body weight.

Until the end of pubertal development, rarely even in adulthood, the increase in adipose mass is determined by hyperplasia of the adipocytes.

This phenomenon is linked to the size of the fat cells, which once reached a critical size (hypertrophy) stimulate the formation of new adipocytes from adipoblasts (hyperplasia).

The number of fat cells can no longer decrease, not even with weight loss; in this way a resistance to weight loss is determined.

Therefore, in the adult, the main mechanism of fat loss lies in the reduction of volume, and not of number, of the single adipocytes.

A subject who became obese before the end of puberty and who subsequently lost weight, even returning to normal, still has a higher number of fat cells.

»Hormones and adipose tissue

Testosterone: reduces the size of adipocytes by promoting lipolysis.

Estrogens: controversial action (lipolytic? Lipogenetic?).

Progesterone: determines an increase in both the number and volume of lipid cells in the lower part of the body (hips, thighs, legs).

Insulin: promotes lipogenesis, inhibits lipolysis and is able to increase both the size and number of adipocytes.

Thyroid hormones: at high doses they have a lipolytic effect to increase energy expenditure.

Catecholamines and GH: lipolytic effect.

Cortisol: increases the volume of adipocytes in the central part of the body.

»Sedentary lifestyle

Effect of technological automation.

Physical activity only on weekends.

Muscle hypotonia and hypotrophy (sarcopenia).

Chronic Psycho-Asthenia.

Paramorphisms: Gibbo, lumbar hyperlordosis, knee valgus, flat foot, ligament laxity.
High FM / FFM, adiposity in the lumbar area, hypothermia, reduced energy expenditure.
Venous insufficiency, fluid retention, exertional tachycardia, orthostatic hypotension.

»Psychological aspects of the obese subject in relation to physical activity

Awareness of one's own inadequacy.

Poor level of physical efficiency.

Embarrassed to show your physique.

Poor coordination and dexterity in movement.

Fear of confrontation.

Natural tendency to hypokinesia and a sedentary lifestyle.

Desire to achieve full physical efficiency.

Desire of reintegration into an "efficient" society.

»Pathologies associated with obesity

Diabetes.

Hypertension.

Dyslipidemia.

Ischemic heart disease.

Amenorrhea and Anovulation.

Endometrial cancer.

Hypogonadism.

Biliary lithiasis and hepatic steatosis.

Respiratory failure.

Osteoarteopathies.

»Physiological limits of the obese subject

Reduced cardio-respiratory function.

Tendency to respiratory acidosis (> blood CO2).

Functional limitations of the musculo-ligament apparatus.

Postural anomalies (in young subjects): valgus knee, lumbar hyperlordosis, cerv kyphosis. dors.

Joint pain syndromes (in adults): gonarthrosis, coxarthrosis, meniscopathies, lumbago, discopathies.

Phlebopathies of the lower limbs.

Inguinal, crural and epigastric hernias.

»Anatomical characteristics of the obese subject

Increased FM / FFM ratio.

Increased abdominal and muscle fat.

Reduced efficiency of muscle fibers II-a compared to II-b.

Reduced muscle capillary flow.

»Metabolic characteristics of the obese subject

Increased circulating FFA.

Reduced lipid beta-oxidation and increased futile cycles.

Hyperinsulinemia with insulin resistance.

Increased glycogenolysis.

Reduced hepatic synthesis of glycogen.

Normal glucose oxidation only at high insulin levels.

Tendency to hyperglycemia.

»Bioenergetic characteristics of the obese subject

TEE = REE + TEF + EEE

TEE: energy expenditure in 24 hours.
REE: energy expenditure at rest.
TEF: food thermogenesis.
EEE: operating energy expenditure.

»Energy expenditure at rest (REE): (from 65% to 75% of the TEE)
(measurable with calorimetry)

Increased by 16% in obese subjects compared to normal weight.

Normal or reduced if we consider only the metabolically active mass

(Kcal REE / Kg FFM: metabolic efficiency index).

»Operating energy expenditure (EEE): 20 - 30% TEE
(measurable in the metabolic chamber)

Increased in the obese subject.

Main determinants:

Type, intensity and duration of physical exercise.
Degree of training and muscle tone.

Degree of obesity.
Genetics.
Sympathetic nervous system.