O-287 Body composition analysis and metabolic monitoring before fertility treatment: hype or hope?
Authors: De Waele E , Blockeel C , Semrl N , Tournaye H , Leemans L , Mackens S , Raeymaekers H 
Published: July 2024

Abstract
The effect of body mass index on both spontaneous and assisted fertility is well known: both lower and high indexes are correlated with negative outcome including live birth rate. Asides the dysmetabolic infertility that can develop by inflammation, insulin resistance and hyperandrogenemia, psychological and social factors deserve attention: a sexual self-image dysfunction is present in up to 20% of obese people with lower sexual desire and arousal.
A positive note is that ART patients want to know about the impact of diet on fertility and ART success, asides the safety of the treatment and coping strategies, when asked about research priorities. Nevertheless, research in the field of preconception weight loss in the case of obesity in non-conclusive. The difference may lay in the strategy followed: lifestyle interventions may differ in approach, new weight-losing drugs might be involved or avoided, and targets and endpoints differ between studies.
A first statement is to be made: body weight is a parameter of the past. In the world of nutrition, BMI is used to describe populations but fails to give accurate information about a single person. Body composition is more refined and can be used in follow-up. Asides dual energy X-ray absorptiometry (DXA), Bio Electrical Impedance Vector Analysis (BIVA) is used to endotype patients. Magnetic Resonance Imaging can, in a whole-body approach, provides very detailed information. In general, fat mass, fat free mass, phase angle (quantitative information) and fat infiltration of muscle (qualitative aspect) are considered ‘the kg of the future’. Associations between higher amounts of fat and poorer ART outcomes are published. As body composition is the result of food intake balanced to total energy expenditure (composed from basal energy expenditure, diet induced thermogenesis and physical activity level), the knowledge of these aspects can form a basis for a personalized approach. Techniques used in clinical practice relevant to this topic are food diary analysis by specialized dietitians (quantitative and qualitative analysis of food intake) and indirect calorimetry. This device will measure oxygen consumption and carbon dioxide production and calculate the basal metabolic rate in kcal/day. The concept of nutrition intake balanced to energy expenditure is validated in critically ill patients where it reduces mortality. It also showed benefit in a cancer population during active treatment.
In a tertiary, university hospital in Brussels, Belgium, the forces of the fertility clinic and the nutrition department were combined: FerMet (Fertility-Metabolism). Patients seeking ART with a BMI &lt;18;5 or higher than 30 are directed. Biophysical endotyping is performed by both metabolic screening, food intake analysis and baseline testing: body composition by BIVA and metabolic measurement by indirect calorimetry. A personalized intervention plan is developed in co-operation with the patient(s) by the dietitian and the supervising MD. Psychological reference or physical activity coaching is initiated if needed. Interim results: a total of 3793 men and woman in 3,5 years. In the population with a BMI below 20, which is only 6.4% of the entire group, body composition analysis reveals: only 9% are confirmed with alarmingly low body fat mass, such as seen in eating disorders. 23% has a fat mass percentage comparable to the general population and 66% represents what is known as ‘constitutional lean’. This might open opportunities to refine criteria to withhold ART based on body weight. In the overweight population, interventions can be tailored on individual metabolic rates and eating patterns, which is unique in the setting of ART. Whole Body MRi can be used in research settings. Benefits of this Biophysical Endotype based interventions to increase fertility outcomes need to be proven by further research.