The study is focused on identification of the link between body size and thermal sensitivity in Calabar, Cross River State, Nigeria. Numerous investigations have been carried out on similar lines in other parts of the world but there is practical dearth of information in this domain of knowledge in the area of study. The subjects/population of this study are adult residents domiciled in the central city of Calabar where urban heat warming is clearly exemplified. The problem statement is predicated on the prevalent urban heat scenario in the area and the general public outcry on the adverse effects of the heat incidence in  the area. From existing literature, it has been recognised that thermal discomfort is to an extent subjective of age, sex and phenotypic make up. Here in this study, three recognised phenotypes have been identified as variables subjects for investigation. They include endomorphs, mesomorphs and ectomorphs. The objective is to elucidate their relative heat sensitivity indices. The justification is viewed from the valuable contributions this study can make to such fields as urban environmental management, individual livelihood sustainability and the general public health benefits. In terms of methodology, the study area has been clearly explained based on its geographical location (sub equatorial, marine coastal belt) weather/climatic characteristics, and so on. The population as stated earlier comprises adult residents domiciled in the Calabar central business district. Population sampling was achieved through a multi stage sampling procedure. The questionnaire instrument was employed in primary data collection, while other surrogate measures was achieved through biophysical data capturing. Data analysis was carried out through hypothesis testing using  one way analysis of variance (ANOVA) following the result. The Fcal ratio stood at 16.960 while the critical value f   stood at 4.51 at 0.05 level of significance. Since Fcal > f  , the null hypothesis was rejected while the alternate hypothesis was accepted this means there is a significant variation in the thermal sensitivity of persons with different phenotype ratios.