Food Energy Conversion

ISSN 0254-4725

Food energy – methods of analysis and conversion factors

FAO FOOD AND NUTRITION PAPER

77

Ingested energy (IE) = gross energy (GE) Faecal energy (FE) Combustible gas (GaE) (from microbial fermentation) Digestible energy (DE) Urinary energy (UE) Surface energy (SE) Metabolizable energy (ME) Heat of microbial fermentation Obligatory thermogenesis, i.e. excess heat relative to glucose during ATP synthesis Net (metabolizable) energy (NME) Non-obligatory dietary thermogenesis Thermogenesis due to effects of cold, drugs, hormones, bioactive compounds or other stimulants Net energy for maintenance (NE) Basal metabolism Physical activity

Food energy – methods of analysis and conversion factors

FAO FOOD AND NUTRITION PAPER

77

Report of a technical workshop Rome, 3–6 December 2002

FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS Rome, 2003

CONTENTS Foreword CHAPTER 1: INTRODUCTION 1.1 Historical background 1.2 Background to the technical workshop 1.3 Rationale for the technical workshop CHAPTER 2: METHODS OF FOOD ANALYSIS 2.1 Analytical methods for proteins in foods 2.2 Analytical methods for fats in food 2.3 Analytical methods for carbohydrates in foods v 1 1 2 4 7 7 11 12

CHAPTER 3: CALCULATION OF THE ENERGY CONTENT OF FOODS – ENERGY CONVERSION FACTORS 18 3.1 Joules and calories 18 3.2 Theoretical framework for an understanding of food energy conversion factors 19 3.3 Flow of energy through the body – a brief overview 20 3.4 Conceptual differences between metabolizable energy and net metabolizable energy 22 3.5 Current status of food energy conversion factors 23 3.6 Standardization of food energy conversion factors 32 3.7 The relationship between food energy conversion factors and recommendations for energy requirements 33 3.8 Other practical implications related to the use of food energy conversion factors 37 CHAPTER 4: SUMMARY – INTEGRATION OF ANALYTICAL METHODS AND FOOD ENERGY CONVERSION FACTORS 57 4.1 Protein 57