Basal Metabolism in Obese Patients
The Harris & Benedict equations return the amount of energy needed to support the basal metabolic rate and daily calorie needs.
These are two mathematical formulas that have been accepted in the medical-scientific field for almost a century, since they were developed back in 1919. During the last 100 years, however, the lifestyle has changed and the percentage of overweight and obese people has changed. markedly increased (the Harris & Benedict formulas do not take into account the subject's lean mass, which is much more metabolically active than fat, but rather the body surface). Consequently, when applied to severely obese or rather muscular individuals, these formulas lose their accuracy.
Several authors have proposed formulas for calculating the basal metabolic rate in obese subjects.
Bernstein et al .:
Basal metabolic rate in obese men: 11.02 * weight (kg) + 10.23 * height (cm) - 5.8 * age (years) - 1032
Basal metabolic rate in obese women: 7.48 * weight (kg) - 0.42 * height (cm) - 3 * age (years) + 844
Lazzer et al. (NB: results expressed in MJ / day, where one megajoule = 238 KCalories):
Basal metabolic rate in obese men: 0.048 * weight (kg) + 4.655 * Height (m) - 0.020 * age (years) - 3.605;
Basal metabolic rate in obese women: 0.042 * weight (kg) + 3.619 * Height (m) - 2.678.
Huang et al .:
RMR = 71.767 - 2.337 * age + 257.293 * sex (woman = 0, man = 1) + 9.996 * weight (kg) + 4.132 * height (cm) + 145.959 * DM (euglycemic = 0, diabetic = 1)
Basal metabolic rate in obese men: (9.99 x weight in kg) + (6.25 x height in cm) - (4.92 x age) + 5.
Basal metabolic rate in obese women: (9.99 x weight in kg) + (6.25 x height in cm) - (4.92 x age) - 161
Why use customized formulas for calculating the basal metabolic rate in obese subjects?
While the opposite is commonly believed, there is little evidence that obese people have an inherently low basal metabolic rate. On the other hand, it has been repeatedly shown that under standard conditions the obese have an absolute higher energy requirement than lean people, due to the greater mass of metabolically active tissues. In fact, weight gain is borne by both fat and lean mass; the latter must in fact adapt to support the greater body weight in the various daily activities. However, this increase is not linear, since the more weight is gained and the more the weight gain is mainly borne by the fat component. Therefore, since the metabolic rate of adipose tissue is much lower than that of muscle, the basal metabolism increases. in a curvilinear way as body weight increases (see figure).
PLEASE NOTE: although in absolute terms (KCal / day) the basal metabolism of obese people is higher than that of people of normal weight, it appears significantly lower in relative terms (KCal / Kg / day), since the percentage of lean mass (metabolically active). It is no coincidence that scholars have known for some time that, when expressed in terms of lean mass, the basal metabolic rate is rather uniform in the population.