People with fat in their thighs and backsides may live longer because the fat traps harmful fatty particles and actively secretes helpful compounds, according to a report published on Tuesday.

Many studies have shown that people who accumulate fat around the abdomen and stomach are more likely to die of heart disease and other causes than bottom-heavy people, but the reasons are not clear.

This may be because several different mechanisms are involved, said Konstantinos Manolopoulos of Britain's University of Oxford.

"It is the protective role of lower body, that is, gluteofemoral fat, that is striking," Manolopoulos wrote in the International journal of Obesity.

"The protective properties of the lower-body fat depot have been confirmed in many studies," he added.

Fat on the bottom and thighs appears to store excess fatty acids, said Manolopoulos, who reviewed published scientific studies for his report.

Pear-shaped people also appear to have lower levels of compounds called inflammatory cytokines -- signaling chemicals involved in the body's response to infection that also can play a role in heart disease and diabetes when they are inappropriately active.

Fat on the legs may also absorb fats from the diet, keeping them from overwhelming the body when people overeat, Manolopoulos said.

Cholesterol levels reflect a tricky balance between high density lipoprotein, the HDL or "good" cholesterol that removes harmful fats from the blood, and low-density lipoprotein, the "bad" LDL cholesterol that can harden and block the arteries.

Fat in the thighs may also be more stable, he said, with studies showing abdominal fat breaks down quickly during fasting or stress, releasing potentially harmful components from the fat.

"The exact regulatory mechanisms of fatty acid release and storage and their effect on short- and long-term fatty acid metabolism remain to be analyzed," Manolopoulos wrote.

Leg fat may also be better at producing hormones such as leptin, which are made by fat and affect appetite and metabolism -- although Manolopoulos said this is poorly understood.

Understanding all this could lead to better drugs for treating obesity and related disease such as diabetes and heart disease, Manolopoulos said.

周二发表的一个报告称，大腿和臀部肥胖的人可能更长寿，因为脂肪吸收了有害的油脂微粒并主动分泌出一种有益的混合物。

许多研究也显示，与下肢肥胖的人相比，腹部和胃部脂肪堆积容更易引起心脏病死亡，原因还不甚清楚。

英国牛津大学的康斯坦丁。马洛普洛斯说："这关系着几种不同的机理。"

马洛普洛斯在国际肥胖期刊文章中写到："下肢臀股的脂肪保护作用很显着。"

他还说："许多研究项已证实，下肢脂肪堆积有保护作用。"

马洛普洛斯在他的报告中，回顾了已发表的研究，研究显示，臀部和大腿的脂肪能储藏过多的脂肪酸。

梨形体型的人体内感染细胞因子水平较低，这是一种人体对感染反映的化学信号，当他们不太活跃时，能有效对抗心脏病和糖尿病。

马洛普洛斯认为，腿部脂肪可以吸收人们日常饮食中过量摄取的脂肪。

胆固醇水平在高密度的脂蛋白之间有一种微妙的平衡，HDL或"好"胆固醇能去除血液中的有害脂肪，低密度的"坏"脂蛋白能够造成动脉血管变硬和堵塞。

他说，大腿的脂肪更稳定，研究显示，节食或有压力时，腹部脂肪分解很快，会释放出有害物质。

马洛普洛斯写到："脂肪酸有节制的精确释放和储存，对长期或短期脂肪酸代谢的影响仍需进一步分析。"

尽管马洛普洛斯说人们对此知之甚少，腿部脂肪也能产生如瘦素，那是一种由脂肪产生的影响食欲和新陈代谢的荷尔蒙。

马洛普洛斯说，完全清楚以后，就能够制造更好的减肥药或治疗相关疾病如糖尿病的药。