BACKGROUND: Because of the limitation of technique, there are few researches on regulating function of central hypothalamus by metabolism, especially the researches on real-time function.OBJECTIVE: To evaluate the response of hypothalamus to oral glucose tolerance test (OGTT) in different body-weighted subjects by using functional magnetic resonance imaging (fMRI) so as to investigate the relationship between the sensitivity of hypothalamus in glycoregulation and disturbance of carbohydrate metabolism.DESIGN: Paired design.SETTING: Department of Radiology and Beijing Geriatrics Institute, Beijing Hospital, National Public Health Bureau.PARTICIPANTS: A total of twenty healthy volunteers were selected from Beijing Geriatrics Institute,National Public Health Bureau, including 10 subjects with obesity (5 males and 5 females; body mass ＞28.0 kg/m2) and 10 subjects with normal body mass (5 males and 5 females; body mass from 18.5 to 23.9 kg/m2). All subjects gave written informed consent before participating in the study.METHODS: fMRI study was performed on GE 1.5 T Signa Twinspeed Infinity with Excite. Each volunteer was ingested of glucose during the fMRI scan. T2* images were acquired using a single-shot gradient echo (EPI) technique. The parameters of EPI included: TR 3 000 ms, TE 40 ms, Flip angle 90 ° , field of view (FOV) 24 cm × 24 cm, thickness 5 mm, gap 0 mm, matrix 64 × 64, number of excitation 1. All 10 subjects with normal body mass underwent a repeat fMRI scan after consuming an equivalent amount of water without glucose on a separate day. The procedure for the fMRI scan with water intake was the same as for glucose ingestion. fMRI data were processed with Intensity Averaging Method.MAIN OUTCOME MEASURES: The central response of hypothalamus and feedback orientation during OGTT in different body-weighted subjects.RESULTS: An acute transient decrease of fMRI intensity in posterior inferior and anterior inferior of hypothalamus was observed in all subjects within 2 minutes after oral glucose intake. This decrease was followed by a recovery to the baseline. However, obese subjects had a delayed intensity decrease [(1.96±1.06) minutes vs. (1.04±0.71) minutes, t =2.14, P ＜ 0.05] and longer recovery time [(26.62±7.35)minutes vs. (16.29±6.42) minutes, t =3.67, P ＜ 0.01] as compared with normal body-weight subjects. Furthermore, decreased fMRI intensity was significant different from baseline intensity [(5.7±2.5)% vs.(14.3±5.5)%, t =2.56, P ＜ 0.05] in obese subjects, but not in normal body-weight subjects. The area of hypothalamus in normal body-weight volunteers demonstrated no significant signal change before and after oral water ingestion (P ＞ 0.05).CONCLUSION: Hypothalamus response to glucose loading is different in normal body-weighted and obese subjects. This suggests that fMRI is a useful tool to evaluate the central regulation of glucose metabolism.