Southerners are thinner than northerners, is it an illusion?
Not really.
In 2017, the "Surveillance Data of Chronic Diseases and Their Risk Factors" released by the Chinese Center for Disease Control showed that the obesity rate in the north was significantly higher than that in the south. In terms of overweight rate, most northern provinces also have higher overweight levels than in the south.
Image source: @人民日报
01 How to tell if you are obese?
Many people judge whether they are fat or not, it may be to look in the mirror to see the body shape, and pinch the stomach to see if there is fat. In fact, none of these practices are accurate.
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At present, one of the standards commonly used internationally to measure whether the human body is overweight, obese, and healthy is to look at the body mass index BMI (BMI), also known as body mass index and body mass index.
BMI is calculated as BMI = weight (kg) ÷ height ²(m), which is your weight divided by the square of your height.
Image source: Dietary Guidelines for Chinese Residents (2022)
According to calculations, a BMI between 18.5-24.0 is a healthy weight.
If the BMI is between 24.0-28.0, it is "overweight"; If the BMI is greater than 28.0, it means "obese".
Some people look a little fat, have fat in their stomachs, or feel that they are fat, not necessarily really obese.
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However, it is necessary to remind everyone that in people with BMI overweight, the heavier the weight, the greater the chance of developing obesity. If you're overweight, start paying attention to control.
02 Factors affecting body weight
Why is that? What factors affect obesity?
1. Genes
Our weight can be affected by genetic factors.
This point is actually easy to see in life, for example, if you see a family, parents are fat, usually children will also be fat. This is genetic inheritance.
2. Metabolism
Metabolism refers to the chemical processes that occur within the body that are necessary to sustain life.
Different people, metabolism will be different, will also affect weight. For example, the body's basal metabolic rate, some people have a high basal metabolic rate, eat the same food and do the same work as you, but consume hundreds of calories higher than you. So you're more likely to be fat, but he won't.
In animals, we often use feed conversion rates to evaluate the efficiency of animal food conversion. In fact, people have a similar effect. Some people's food energy conversion rate is high, such as eating the same food, you convert into energy stored in the body more than others, you are more likely to be fat.
3. Age
As we age, body composition and basal metabolism change, such as the body's energy metabolism rate will become smaller, physical activity will decrease, and weight will also be affected.
4. Disease
Some diseases can also affect weight changes, such as anorexia nervosa, chronic hepatitis, cirrhosis, cancer, which can lead to weight loss.
5. Diet
If we eat more, especially high-fat, high-sugar, high-energy foods, such as fried chicken, chips, etc., too much energy will make us gain weight.
6. Physical activity
Physical activity, such as running, brisk walking, and even doing housework, drains energy in the body. But if you are less physically active and have too little energy expenditure, you will also gain weight .
03 Why are northerners fatter than southerners?
According to the Surveillance Data of Chronic Diseases and Their Risk Factors, the top 5 provinces with obesity rates in mainland China are:
First Beijing 25.9
Second Hebei 22.2
Third Xinjiang 21.5
Fourth Tianjin 21.2
5th Heilongjiang 19.8
Basically all are northern provinces.
The provinces with the lowest obesity rates are Guangxi, Hainan, Tibet, Guizhou and Sichuan, which basically belong to the southwest region. Therefore, it is not an illusion that southerners are thinner than northerners, but an objective fact.
Why? How are people from North and South different?
1. Different diets
Northerners eat more pasta, and southerners eat more rice.
While they are both carbohydrates themselves, one harsh reality is that people who eat pasta are indeed more likely to gain weight.
A study by Xi'an Jiaotong University investigated and analyzed more than 100,000 middle-aged and elderly people in the northwest region of the mainland and found that people who like to eat noodles have a higher risk of obesity than people who like to eat rice. This is especially true in men.
Data analysis found that replacing wheat with rice of the same frequency and weight (5 times per week) was significantly associated with a 36.5% reduction in the risk of excess body fat in normal-weight men and a 20.5% reduction in the risk of central obesity in normal-weight women.
Why?
On the one hand, wheat protein and rice protein have different effects on metabolism. In addition to carbohydrates, wheat and rice have small amounts of protein that have different effects on fat metabolism.
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Wheat seeds are mainly gluten protein, and some studies have suggested that gluten protein may promote weight gain by reducing tissue thermogenesis and reducing energy expenditure. Rice protein may increase the effect of lipolysis by inhibiting fat synthesis.
On the other hand, pasta and rice also have different energy densities.
Rice is more absorbent of water, so the moisture content of rice is large, and the calories of rice are lower under the same weight; But the water content of steamed buns and flower rolls is only about 45%-50%, flapjacks are lower, less moisture, high calorie density, a little more bite, the intake of calories is a lot more.
2. The climate is different
Everyone knows that temperatures in the north are generally lower and colder, which may also be an assist for obesity.
The weather in the north is cold early and longer-lasting, and in the extremely cold Heilongjiang, winter can even last for about half a year.
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In cold weather, our bodies instinctively store more calories and are more willing to eat hot and high-calorie foods to resist the cold, which is why there is a tradition of "sticking autumn fat" in autumn.
In addition, when the weather is cold, people's chances of going to outdoor sports will also drop significantly, and most of the time they will stay at home, forced to eat more, move less, and naturally make it easier to gain weight. The south usually has high temperatures, the body's energy metabolism is faster, and the time to exercise outdoors throughout the year is more and longer, so it is naturally not so easy to gain weight.
Bibliography:
[1] Dietary Guidelines for Chinese Residents (2022)
[2] Surveillance Data on Chronic Diseases and Their Risk Factors
[3] Xu K, Zhang B, Liu Y, Mi B, Wang Y, Shen Y, Shi G, Dang S, Liu X, Yan H. Staple Food Preference and Obesity Phenotypes: The Regional Ethnic Cohort Study in Northwest China. Nutrients. 2022 Dec 9;14(24):5243. doi: 10.3390/nu14245243. PMID: 36558402; PMCID: PMC9784345.
[4] Santos, S.H.; et al. Wheat gluten intake increases weight gain and adiposity associated with reduced thermogenesis and energy expenditure in an animal model of obesity. Int. J. Obes. 2016, 40, 479–486.
[5] Yang, Lin et al. “Rice protein improves adiposity, body weight and reduces lipids level in rats through modification of triglyceride metabolism.” Lipids in health and disease vol. 11 24. 13 Feb. 2012, doi:10.1186/1476-511X-11-24
[6] Luan Hui, Yang Lin. Research Progress on Rice Protein Regulating Cholesterol Metabolism[J]. Science and Technology of Food Industry, 2012, 33(5):4.
Author: Ruan Quang Feng, Director of Science and Technology Department, Kexin Food and Nutrition Information Exchange Center
Reviewed: Huilian Zhu, Head Professor, Department of Nutrition, School of Public Health, Sun Yat-sen University