The dynamics of human body weight change

TL;DR

This paper presents a comprehensive mathematical model of human weight change based on macronutrient fluxes, revealing two distinct dynamic behaviors and emphasizing the importance of understanding these for effective obesity treatments.

Contribution

It introduces a unified mathematical framework for long-term human weight dynamics, encompassing all previous models as special cases.

Findings

Two classes of body composition dynamics identified

Perturbations can produce similar responses in both classes

Existing data cannot distinguish between the classes

Abstract

An imbalance between energy intake and energy expenditure will lead to a change in body weight (mass) and body composition (fat and lean masses). A quantitative understanding of the processes involved, which currently remains lacking, will be useful in determining the etiology and treatment of obesity and other conditions resulting from prolonged energy imbalance. Here, we show that the long-term dynamics of human weight change can be captured by a mathematical model of the macronutrient flux balances and all previous models are special cases of this model. We show that the generic dynamical behavior of body composition for a clamped diet can be divided into two classes. In the first class, the body composition and mass are determined uniquely. In the second class, the body composition can exist at an infinite number of possible states. Surprisingly, perturbations of dietary energy intake or energy expenditure can give identical responses in both model classes and existing data are insufficient to distinguish between these two possibilities. However, this distinction is important for the efficacy of clinical interventions that alter body composition and mass.