《油脂对肥胖的关系不大》

（与Brucc A等先生商榷)

黄学章（2021/11/8）

Brucc A等先生在由其编写的《貝雷，油脂化学与工艺学》第七章，第四节中写道：

“尽管人们对肥胖的原因理解疑问重重，但仍有证据显示，造成肥胖的慢性能量代谢不平衡大部分由脂肪的热量引起（4.1引言)”。

“饮食中脂肪的饱腹感差，会有选择地引起肥胖。与碳水化合物，蛋白质，酒精不同，人体对于脂肪的氧化代谢调控较差。饮食中增加的脂肪不会加速它自身的氧化，而是促进多余的脂肪向脂肪组织中的储存。

所以脂肪是造成长期能量正平衡，与肥胖相关的主要饮食因素。（4.7结论)”。

上述文字的意思是，肥胖是由于过度摄入脂肪引起，理由是：

1，因为脂肪的饱腹感差，可能误以为还没吃饱，而过度饮食，导致肥胖。

2，脂肪摄入过量，多余的脂肪不能被氧化消耗掉，被储存到脂肪组织中，导致肥胖。

3，人体对脂肪氧化代谢的调控能力比碳水化合物，蛋白质差。因此，人体生理活动所需要的能量，优先从糖和蛋白质氧化代谢获取，而脂肪的氧化代谢则被滞后，忽视，从而导致脂肪积累形成肥胖。

然而，这些论断是值得商榷的。

1，脂肪的饱腹感差，并不一定导致过度饮食，这只是个饮食习惯问题而已。

2，从外部摄入的动植物脂肪，是不能直接储存起来的。人体储存的，必须是自己合成的各自独特的脂肪。

正如德国哲学家莱布尼茨所说:“世上没有两片完全相同的树叶”。每个人的脂肪结构特点也都不会完全相同，更不可能直接储存动植物脂肪。

3，脂肪与糖（淀粉)和蛋白质的氧化代谢途径基本上是一致的。都是先转化为乙酰辅酶A，再通过“三羧酸循环”，彻底氧化为二氧化碳和水，并放出能量。

油脂含有羧基和双键活性基团，氧化代谢的速度和“可控性”，应该高于糖类和蛋白质，而不是低于……。

所以，人体在体力脑力活动时，所需的能量，优先是来自于脂肪的氧化代谢，其次才是来自糖和蛋白质。

否则，如果是优先消耗糖，蛋白质，后消耗脂肪，那么健美运动员去掉的将是肌肉，留下的是脂肪，也就不可能有健美运动了。同样，通过运动减肥也就无法成功。

本人4年多来，每天早晨空腹喝40毫升植物油，的确没有饱腹感，然后连续，快速步行近一个小时，体力依然充沛，还未感到饥饿。这说明脂肪既能快速消化吸收，又能快速氧化代谢释放能量。

因此一座可调控的，收支灵活的，能量效率高的脂肪库，才是人体所必须的。

而肥胖，则是由于摄入碳水化合物、蛋白质、动植物脂肪等营养物质总量过剩而造成。

多余的营养物质经过消化吸收，再在肝脏或肠壁内，合成为人体脂肪储存起来。只要总摄入量有所控制，人体脂肪储存不致过量，就不会引起肥胖。

在人体脂肪的合成过程中，碳水化合物、蛋白质以及动植物油脂同样都是合成材料。而从碳水化合物得到的葡萄糖，却是较为主要的材料，动植物油脂反而居于次要。而且动植物油脂的摄入量又远低于碳水化合物的摄入量。

也就是说，摄入过量脂肪，并不比摄入过量碳水化合物，以及过量蛋白质更容易导致肥胖。

根据“貝雷”书中介绍，“美国心脏协会”推荐，人体摄入脂肪能量应为不高于总摄入能量的30%。

如以成人日消耗能量为1800～2200千卡/天估计，每天摄入油脂应为60～73.3克。

因此，“中国居民膳食指南”推荐25～30克/天是远不够的。

（附英文）

《Fat has little to do with obesity》

(discuss with Mr. Bruce a, etc.)

Huang Xuezhang 

(November 8, 2021)

Mr. brucc a et al. Wrote in Chapter 7, section 4 of 《Bailey, oil chemistry and technology 》prepared by him:

"Although people have many doubts about the causes of obesity, there is still evidence that the chronic imbalance of energy metabolism causing obesity is mostly caused by the calories of fat (4.1 introduction)".

"The poor satiety of fat in the diet will selectively cause obesity. Unlike carbohydrates, protein and alcohol, the human body has poor regulation of fat oxidation and metabolism. The increased fat in the diet will not accelerate its own oxidation, but promote the storage of excess fat into adipose tissue.

Therefore, fat is the main dietary factor causing long-term positive energy balance and obesity. (4.7 conclusion) ".

The above words mean that obesity is caused by excessive intake of fat for the following reasons:

1. Due to the poor satiety of fat, you may mistakenly think you are not full and overeat, resulting in obesity.

2. Excessive fat intake, excess fat can not be oxidized and consumed, and is stored in adipose tissue, leading to obesity.

3. The human body's ability to regulate the oxidative metabolism of fat is worse than that of carbohydrate and protein. Therefore, the energy required for human physiological activities is preferentially obtained from the oxidative metabolism of sugar and protein, while the oxidative metabolism of fat is delayed and ignored, resulting in fat accumulation and obesity.

However, these conclusions are debatable.

1. Poor satiety of fat does not necessarily lead to overeating, which is just a problem of eating habits.

2. Animal and vegetable fats taken from the outside cannot be stored directly. What the human body stores must be their own unique fats synthesized by themselves.

As the German philosopher Leibniz said, "there are no two identical leaves in the world". Everyone's fat structure characteristics will not be exactly the same, let alone directly store animal and plant fat.

3. The oxidative metabolic pathways of fat, sugar (starch) and protein are basically the same. They are first converted to acetyl coenzyme A, and then completely oxidized to carbon dioxide and water through the "tricarboxylic acid cycle" and release energy.

Oil contains carboxyl and double bond active groups. The speed and "controllability" of oxidative metabolism should be higher than that of sugars and proteins, not lower than.

Therefore, when the human body is engaged in physical and mental activities, the energy required first comes from the oxidative metabolism of fat, followed by the oxidation of sugar and protein.

Otherwise, if the priority is to consume sugar and protein ,the last is fat , then the bodybuilders will remove the muscle and leave the fat, so there can be no bodybuilding. Similarly, losing weight through exercise will not be successful.

For more than four years, I drink 40ml vegetable oil on an empty stomach every morning. I really don't feel full. Then I walk continuously and quickly for nearly an hour. I'm still energetic and haven't felt hungry. This shows that fat can not only digest and absorb quickly, but also oxidize and metabolize quickly and release energy.

Therefore, a fat bank with adjustable, flexible revenue and expenditure and high energy efficiency is necessary for the human body.

Obesity is caused by the excess of total nutrients such as carbohydrate, protein, animal and plant fat.

After digestion and absorption, the excess nutrients are synthesized into human fat in the liver or intestinal wall and stored. As long as the total intake is controlled and the human fat storage is not excessive, it will not cause obesity.

In the process of human fat synthesis, carbohydrates, proteins and animal and vegetable oils are also synthetic materials. Glucose obtained from carbohydrates is the dominant material, while animal and vegetable oils are secondary. Moreover, the intake of animal and vegetable oils is far lower than that of carbohydrates.

In other words, eating too much fat is not more likely to lead to obesity than eating too much carbohydrates and too much protein.

According to the introduction in Bailey's book, the American Heart Association recommends that the body's fat energy intake should not be higher than 30% of the total energy intake.

If it is estimated that the daily energy consumption of adults is 1800 ~ 2200 kcal / day, the daily intake of oil should be 60 ~ 73.3 G.

Therefore, it is far from enough to recommend 25 ~ 30g / day in the "dietary guidelines for Chinese residents".