Caloric Deficiency in the Diet Below PPM - Causes of Functional Disturbances

Primary metabolism, also known as PPM, is the amount of energy required to maintain basic life processes such as breathing, system functions, regulating body temperature, and regeneration processes. PPM is the most significant component of a person's daily energy needs and its value depends on several factors, such as gender, age, weight, and muscle mass. The greater the body weight, the higher the PPM value. Women typically have a PPM value that is a few percentage points lower than men due to their lower muscle mass. To estimate the PPM value, several variables need to be taken into account.

The PPM value can be computed using accessible formulas, most commonly the Harris-Benedict and Mifflin-St. Jeor formulas. In a study conducted by Miller S., Milliron B. J., Woolf K. U., PPM values were measured in 38 women using indirect calorimetry. The study found that the application of the aforementioned formulas resulted in an overestimation of PPM values compared to the outcomes achieved using the calorimetry method. The most precise formula was proposed by Owen O. E. and his colleagues.

PPM = 795 + 7,18 × body mass [kg].

PPM = 50,4 + 21,1 × body mass [kg] Weijs P. J. and ten Haaf T. conducted a similar study involving amateur athletes. The study found that the Cunningham pattern of fat-free body weight (FFM) was most suitable for individuals who are very physically active. PPM = 95,272 × FFM [kg] + 2026,161 Individuals who engage in sports for recreation and wish to reduce their body fat can use the Harris-Benedict, Mifflin-St. Jeora pattern or derive an average from the results of various available patterns. PPM is the largest but not the only component of daily energy requirements.

CPM is the quantity of kilocalories expended daily, taking into account not only PPM but also the energy utilized in daily movement. The recommendations presented in the Nutrition Standards for the population of Poland are still current. The level of physical activity (PAL) should be evaluated taking into account 3 levels. Low activity – PAL: 1.4–1.69Moderate activity – PAL: 1.7–1.99High activity – PAL: 2.0–2.4 CPM is calculated based on the formula: PPM × PAL. The resulting CPM value constitutes the daily energy requirement, the fulfillment of which allows maintaining the current body weight. Therefore, if we want to decrease fatty tissue, it is necessary to reduce the ingested kilocalories. However, it is not a good idea to lower the caloric intake of the diet below the PPM level. Why?

PPM is essential for the proper functioning of the body, particularly for maintaining an appropriate level of physical activity. Even when the goal of a diet is weight loss, additional energy is still required, which constitutes about 10% of the total metabolic requirement. PPM values are also necessary to provide adequate energy for digestion, absorption, and metabolism of nutrients. However, if the goal is weight loss, it should be taken into account that consuming foods with low calorie content may lead to a significant reduction in CPM. In the study by Müller M. J. et al., participants consumed a diet with 50% fewer calories than their daily total requirement for three weeks. The results of this study showed that participants lost an average of 6 kg of body weight, but also lost 159 g of fat-free mass per day and 114 g of fat per day. Furthermore, participants regained weight quickly after returning to a diet with more calories. The results of this study show that low-calorie diets can lead to a loss of fat-free mass such as muscles and not just fat. Moreover, low-calorie diets are very difficult to balance, as they must provide adequate amounts of nutrients and vitamins to avoid a deficiency. In the study by Davoodi S. H. et al., the effects of a several-week restrictive diet were compared with a diet with variable calorie intake. Participants in group one consumed an average of about 1200 kcal per day, while participants in group two alternately followed a restrictive diet (1400 kcal/day) and a diet without restrictions – they could eat according to their preferences for three days (an average of 2000 kcal/day). Resting metabolic rate in both groups did not differ significantly in the first three weeks of the experiment. In the third week, the resting metabolic rate in group one dropped dramatically and decreased significantly compared to the resting metabolic rate in group two. The results of this study show that low-calorie diets can lead to a significant reduction in CPM, which can lead to weight loss, particularly of fat-free mass such as muscles.