*Magnetic Resonance Centre, Institute of Cellular Medicine, Newcastle University, Newcastle upon Tyne, U.K.
†Diabetes Trials Unit, University of Oxford, U.K.
Clin Sci (Lond). 2015 Apr;128(7):405-10. doi: 10.1042/CS20140553.
Type 2 diabetes (T2DM) is frequently regarded as a disease of obesity and its occurrence in individuals of normal body mass index (BMI) is often regarded as indicating a non-obesity-related subtype. However, the evidence for such a distinct, common subtype is lacking. The United Kingdom Prospective Diabetes Study (UKPDS) cohort of people diagnosed with T2DM in the 1970s and 1980s had a median BMI of only 28 kg/m2. UKPDS data form the basis of current understanding of the condition even though one in three of those studied had a BMI of less than 25 kg/m2. BMI, though, is a population measure and not a rigid personal guide. Weight loss is considered de rigueur for treating obese diabetic individuals, but it is not usually considered for those deemed to have a normal BMI. Given the new evidence that early T2DM can be reversed to normal glucose tolerance by substantial weight loss, it is important to explain why non-overweight people respond to this intervention as well as obese individuals. We hypothesize that each individual has a personal fat threshold (PFT) which, if exceeded, makes likely the development of T2DM. Subsequent weight loss to take the individual below their level of susceptibility should allow return to normal glucose control. Crucially, the hypothesized PFT is independent of BMI. It allows both understanding of development of T2DM in the non-obese and remission of diabetes after substantial weight loss in people who remain obese by definition. To illustrate this concept, we present the distribution curve of BMI at diagnosis for the UKPDS cohort, together with a diagram explaining individual behaviour within the population. The concept of PFT is of practical benefit in explaining the onset of diabetes and its logical management to the non-obese majority of people with T2DM.
2 型糖尿病（T2DM）通常被认为是肥胖症的一种疾病，而在正常体重指数（BMI）的个体中发生 T2DM 通常被认为表明存在一种非肥胖相关的亚型。然而，缺乏这种明确、常见亚型的证据。20 世纪 70 年代和 80 年代被诊断出患有 T2DM 的英国前瞻性糖尿病研究（UKPDS）队列的人群的 BMI 中位数仅为 28kg/m2。尽管研究中有三分之一的人的 BMI 低于 25kg/m2，但 UKPDS 数据仍然是当前对该疾病理解的基础。然而，BMI 是一个群体指标，而不是个人的硬性指标。减肥被认为是治疗肥胖糖尿病患者的必要措施，但对于那些被认为 BMI 正常的患者通常不会考虑减肥。鉴于新的证据表明，早期 T2DM 可以通过大量体重减轻恢复正常血糖耐量，解释为什么非超重人群也像肥胖人群一样对这种干预有反应是很重要的。我们假设每个人都有一个个人脂肪阈值（PFT），如果超过这个阈值，就有可能发展为 T2DM。随后的体重减轻使个体低于其易感性水平，应该可以恢复正常的血糖控制。至关重要的是，假设的 PFT 与 BMI 无关。它既能解释非肥胖人群中 T2DM 的发生，也能解释肥胖人群在大量体重减轻后糖尿病的缓解，因为肥胖人群的定义就是肥胖。为了说明这一概念，我们展示了 UKPDS 队列的诊断时 BMI 分布曲线，并附有一个解释人群中个体行为的图表。PFT 概念对于向非肥胖的大多数 T2DM 患者解释糖尿病的发生及其逻辑管理具有实际意义。
