Adaptation or Maladaptation? Rethinking How Energy Restriction Outcomes Are Monitored

Energy restriction (ER) serves as both a corrective health measure in metabolically compromised individuals and as a strategically implemented tool to enhance athletic performance and/or meet sporting weight divisions. Individuals with overweight/obesity who embark on a weight loss intervention often experience temporal improvements in metabolic health, only to be undermined by the phenomenon known as adaptive thermogenesis, and subsequent weight regain. ER in elite sport settings, whether a deliberate strategy to manipulate body composition or an unintentional failure to meet the high energy demands of intense training, can also trigger a cascade of adaptive yet energy-conserving measures across biological systems, tissues, and organs, ultimately compromising long-term health. Despite two comparatively different goals, these populations share one common requirement: a sensitive monitoring tool. Predicting problematic ER, however, remains challenging. Contemporary tools employed by practitioners and healthcare providers often suffer from a diagnostic latency, capturing 'whole-body' maladaptations only after they have passed the point of effective corrective input. In this Current Opinion, we propose that metabolomics-the comprehensive analysis of all metabolites in a biological sample-may represent a promising tool to help identify the transition from adaptation to maladaptation by capturing subtle biochemical shifts that precede whole-body changes. We explain how both populations could utilise this tool to identify when ER needs to be corrected to prevent physiological decline and protect long-term health.