Digestible and Metabolizable Energy Intake in Humans: a Systematic Review

Area of Science:

• Human nutrition
• Energy metabolism

Background:

• Digestible energy intake (DEI) and metabolizable energy intake (MEI) are crucial for understanding human energy balance.
• DEI accounts for fecal energy loss, while MEI also includes urinary energy loss.

Purpose of the Study:

• To systematically review studies measuring DEI and/or MEI using bomb calorimetry.
• To synthesize findings on factors influencing energy absorption, including diet and health status.

Main Methods:

• Systematic literature search of MEDLINE, Cochrane Library, CINAHL, and Scopus (1973-2024).
• Inclusion of human studies (adults ≥18 years) using bomb calorimetry for DEI/MEI measurement.
• Descriptive summary of data across various dietary conditions and health statuses.

Main Results:

• Overeating increased fecal energy losses, but proportional DEI/MEI remained stable, indicating adaptation.
• High-fiber diets and tree nuts reduced DEI/MEI proportions, showing dietary composition impacts energy absorption.
• Aging and diseases (e.g., short bowel syndrome) were linked to significantly reduced DEI/MEI proportions.

Conclusions:

• Dietary quantity and composition significantly influence energy absorption efficiency.
• Aging and certain diseases impair the body's ability to absorb energy.
• Further research with standardized protocols and RCTs is needed to clarify DEI/MEI determinants.