Once upon a time, for a Chinese man, having a protruding belly indicates a prestigious status— rich, mature, and sometimes ignorant. People feel kind of proud to have a big stomach and lightly attribute it to the beer they’re enjoying.

Is it true that drinking beer causes their large waists, or perhaps their ignorance does it?

Despite of numerous anecdotes, unfortunately, the fact is, we don’t know! The correlation between alcohol intake and body weight remains obscure till now, let alone causation.

One should be cautious when reading and interpreting current health literature. It is very common to see statements like “drinking alcohol is not related to body weight”, or “three cups of milk a day reduces your weight.” Common people tend to ignore the fact that most studies employ multivariate models to obtain the claimed odds ratio or relative risk ratio. How people adjust the models is very important. In alcohol studies, alcohol intake is often adjusted for total energy intake. Thus, the correct interpretation for a “null alcohol effect” should be “given the same amount of energy intake, there is no additional alcohol effect on body weight.”

By saying this, it is very reasonable to ask, “what’s the relationship between alcohol intake and subsequent or concurrent food intake?”

It is possible that people eat more when they drink alcohol, or vice versa. In the western society, many people drink alcohol before taking the main course of foods. Studies have shown that alcohol intake may increase the amount of food intake by increasing appetite, but again, the opposing evidence also exists. In fact, large cohort studies such as the Nurse Health Study suggested that alcohol intake was related to a lower body weight in the long run. My personal experience is that I can’t eat the usual amount of foods when I drink (even just one cup), but I don’t like alcohol. Furthermore, I found it disturbing when I am drinking alone. I tend to eat lots of junk snack–which is energy too.

Then, what’s the biological value of alcohol intake? We all know that alcohol is one type of “empty energy” which means pure energy without other nutrition value (like pure sugar). However, we’ve all experienced (and indeed biologically proved) that alcohol intake will increase oxidation in our body, for example, thermogenesis (heat), perspiration, urination, and fuzzy mind. Strictly speaking, human body spends more energy after alcohol intake. In a sense, alcohol is one of the most efficient energy stimulants human can find.

Finally, how does alcohol intake relate to other lifestyle/personal behavior? It is well known that heavy alcohol drinking positively correlates with smoking, and smoking is related to a lower body weight. Further, what about physical activities, food patterns or food composition? Do people eat more animal products when they drink alcohol than when they don’t?

The above questions lead to our discussions on culture differences between Chinese society and American society. In China, people drink beer during a gathering accompanied by copious foods. Even when drinking alone, people tend to have something to go with it. There is even a name for it— “appetite drinking”.
On the other hand, western people tend to drink alcohol without any foods (but during a fest, people also eat a lot of hotdogs and pizza). In addition, the type of alcohol is also important. When drinking a beer during dinner, people tend to eat at least the usual amount of foods, and perhaps more foods, while during a social gathering people drink liquid and eat a smaller amount of foods. In most cases, overall food intake may be less than usual when drinking before eating.

Therefore, the relationship between beer and heavy stomach may arise from the over-intake of foods, especially among Chinese.

Furthermore, when we talk about fat deposit, we should distinguish subcutaneous fat (under the skin) and visceral fat (deep inside fat) around waist. These can be measured by CT or MRI. Studies have found that there is a disproportionally higher visceral/subcutaneous fat ratio among Asians than among Caucasians. That is, Caucasians not only put a lot of weight on their waist, but also put weight elsewhere like back and butt, while Asian men tend to deposit extra fat around their waist. Thus the same waist may cause more harm among Asians than among Caucasians.

The detrimental effects of having a large visceral fat are still hypothetical but some are supported by biological experiments. For example, the adipocytes (fat cells) in visceral fat are more metabolically active than those in subcutaneous fat. There are more blood vessels around them too. Thus, visceral fat deposit is more mobile than subcutaneous fat. The free fatty acids are more likely to move in and out of visceral fat, causing a heavier load on insulin and liver. In addition, fat cells are not passive storage box, they are regulators. The signals sent out by these adipocytes are generally not good (in the setting of modern human body) because most of them are asking for more energy expenditure to use up the deposited fat. But we just can’t use up all these extra energy!
Why do Asian men have to suffer this? Maybe Chinese people have subject to a different evolution stress during past tens of thousands of years?

Chinese have been in a stable agriculture society for a long time. A stable food supply by agriculture steadily increased population although ancient Chinese were often in semi-starvation. The average energy intake among ancient Chinese was lower than those among Caucasians because Chinese emphasized on vegetable foods rather than animal products. This lower energy intake might selectively create a gene profile which was very thrift in conserving energy.

On the other hand, agriculture makes food supply predictable. For ancient Chinese, there was no need to worry too much about foods because they could store foods and there would be foods available in a foreseeable future (e.g., within months). So Chinese didn’t develop a tendency to deposit energy for long term (such as in subcutaneous fat). Instead, extra energy is stored in the tummy so that it is readily available to be used. Maybe storing fat in the tummy is evolutionally earlier than storing fat in the back and butt.