The use of phase analysis techniques to assess left ventricular mechanical dyssynchrony (LVMD) has been well documented. However, artifacts have reduced the accuracy of the assessment due to soft tissue attenuation, so little information is available about the effects of obesity on LVMD. The aim of this study was to evaluate LVMD in patients with simple obesity by SPECT with a new cadmium-zinc telluride (CZT) detector and to explore the effects of obesity on left ventricular wall motion. We retrospectively analyzed 95 patients with myocardial perfusion imaging (MPI) images without perfusion defects, of which 55 were diagnosed with simple obesity (BMI > 30), and 40 non-obese patients (BMI < 25) matched for age and sex were used as controls. The five-point method was used to analyze the MPI images of the two groups, and the complete cardiac function parameters including phase bandwidth (PBW) and phase standard deviation (PSD) were obtained. Although the PBW values of the two groups were within the normal range (cut-off value > 90°), the PBW (35.4 ± 28 vs 24.9 ± 7.5, P < .001; 36.6 ± 18.4 vs 28.7 ± 9.1, P = 0.01) and PSD (8.7 ± 7.6 vs 5.9 ± 2, P = 0.02; 9.2 ± 4.9 vs 7.1 ± 2.7, P = 0.01) of the obese group were larger than the control group under both stressing and resting, and the difference was statistically significant. CZT-SPECT can effectively assess LVMD in obese patients, and they are more likely to develop LVMD, which may be related to their left ventricular volume.