Weight neutral approaches are experiencing a rapid growth period in research right now, although the foundational work began in the 1950s when intentional weight loss was first recognised as unlikely to be sustained, and social justice movements during the 1960's recognised clear discrimination against people with larger bodies.
These academic articles will get you started:
GENERAL OVERVIEWS OF SIZE ACCEPTANCE VS WEIGHT CENTRIC PERSPECTIVETylka, Tracy L., et al. "The weight-inclusive versus weight-normative approach to health: Evaluating the evidence for prioritizing well-being over weight loss." Journal of Obesity 2014 (2014).
Bombak, Andrea. "Obesity, health at every size, and public health policy." American journal of public health 104.2 (2014): e60-e67.
Hunger, Jeffrey M., Smith, Joslyn P., and Tomiyama, A. Janet. "An Evidence‐Based Rationale for Adopting Weight‐Inclusive Health Policy." Social Issues and Policy Review 14.1 (2020): 73-107.
Tomiyama, A. Janet, et al. "How and why weight stigma drives the obesity ‘epidemic’ and harms health." BMC medicine 16.1 (2018): 123.
Dollar, Emily, Margit Berman, and Anna M. Adachi-Mejia. "Do no harm: Moving beyond weight loss to emphasize physical activity at every size." Preventing chronic disease 14 (2017).
O'Hara, Lily, and Jane Taylor. "Health at every size: A weight-neutral approach for empowerment, resilience and peace." International Journal of Social Work and Human Services Practice 2.6 (2014): 272-282.
SYSTEMATIC REVIEWS OF WEIGHT NEUTRAL INTERVENTIONS
Clifford, Dawn, et al. "Impact of non-diet approaches on attitudes, behaviors, and health outcomes: A systematic review." Journal of Nutrition Education and Behavior 47.2 (2015): 143-155.Schaefer, Julie T., and Amy B. Magnuson. "A review of interventions that promote eating by internal cues." Journal of the Academy of Nutrition and Dietetics 114.5 (2014): 734-760.
Ulian, M. D., et al. "Effects of health at every size® interventions on health‐related outcomes of people with overweight and obesity: a systematic review." Obesity Reviews (2018).