People in romantic relationships who show a high-K fitness profile are more likely to be “good” patients

A study of individuals with a medical diagnosis in Romania found that individuals with high-K fitness who were in a romantic relationship were much more likely to be activated patients—i.e., to take an active role in managing their health (“good” patients). This association was even more pronounced in individuals who were satisfied with their romantic relationships. The research was published in Frontiers in Psychology.

Life history theory is a biological and evolutionary framework that explains how organisms allocate limited time and energy to growth, reproduction, and survival. It focuses on trade-offs between these competing demands across the lifespan. The theory proposes that there are two strategic approaches organisms can adopt: K-selected (or slow) strategies and r-selected (or fast) life history strategies.

K-selected or slow life history strategies describe patterns adapted to stable environments where populations are close to carrying capacity (i.e., the maximum numbers their environment can support). These strategies involve slow development, delayed reproduction, low fertility, high parental investment, and long lifespans.

Fast or r-selected strategies describe life-history patterns adapted to unstable or unpredictable environments. They involve early reproduction, high fertility, low parental investment, faster development, and shorter lifespans. Rather than being discrete categories, K- and r-selection are best understood as endpoints of a continuum.

In psychology and human research, these concepts are often applied metaphorically to individual differences in behavior and decision-making. This is where the term K-fitness appears. K-fitness refers to reproductive and survival success under K-selected conditions, emphasizing efficiency, long-term planning, and investment in quality over quantity. Individuals high in K-fitness tend to prioritize stability, health maintenance, and sustained social relationships.

Study author Cristina Ene and her colleagues wanted to explore how life history strategies relate to health behavior. They hypothesized that individuals with slow life history strategies (high-K strategies) would tend to be “good” patients who prioritize and value their health. They expected that this would be even more apparent if they were in a good romantic relationship.

Study participants were 252 individuals between 19 and 97 years of age. Their average age was 39 years, and 68% were women. They were required to have a medical diagnosis and to be in a committed relationship.

Participants’ activity in the role of a patient was assessed using the Patient Activation Measure. Their adherence to a high-K fitness strategy (i.e., slow life history strategy) was assessed using the High-K Strategy scale.

Study participants also completed assessments of pain catastrophizing (the Pain Catastrophizing Scale) and satisfaction with their romantic relationship (the Relationship Assessment Scale). Pain catastrophizing is a maladaptive cognitive–emotional response to pain characterized by persistent thinking about pain (rumination), magnification of pain-related threat, and feelings of helplessness.

Results showed that individuals who adhered more to a high-K fitness strategy tended to be more active as patients—i.e., they took more care of their health and adhered to treatment regimens. They also tended to be more satisfied with their relationships and were less prone to pain catastrophizing.

Further analyses suggested that a high-K fitness strategy leads to less pain catastrophizing, and that lower pain catastrophizing improves patient activation (i.e., leads individuals to adhere more to treatment plans for their medical condition). In individuals who were more satisfied with their relationship, this association between high-K fitness strategy and patient activation was even stronger.

“In this study, we can highlight again the importance of life history as a general framework for orientation in the way the individual chooses to mobilize his resources according to a cost–benefit analysis for success that he makes regarding his resources. We can also extract from this study the importance of a satisfactory couple relationship in the process of recovery from the disease, and this has a motivating role,” study authors concluded.

The study contributes to the scientific understanding of the links between life history strategy and health-related behaviors. However, it should be noted that the design of this study does not allow any causal inferences to be derived from the results.

The paper, “Life history strategy and romantic satisfaction in patients’ behavior,” was authored by Cristina Ene, Vlad Burtaverde, Peter Karl Jonason, Felix Brehar, and Viorel Pruna.