Lifestyle and Obesity: How Smoking and Sleep Habits Affect Your Weight

**Lifestyle Factors**

**1. Smoking and Obesity**

Some people say that quitting smoking will cause weight gain. Modern medical research has shown that there is some truth to this claim.

Cigarettes contain nicotine, tar, and other toxic substances, including benzene compounds. Smoke entering the lungs can cause coughing, and in certain individuals, it can even lead to lung cancer. Smoke entering the stomach stimulates intestinal peristalsis, enhancing digestion; however, prolonged exposure to smoke can suppress appetite and cause weight loss.

Quitting smoking is generally a good thing, but for many long-time smokers, it's a huge challenge. Research from the U.S. Centers for Disease Control and Prevention (CDC) shows that Americans gain weight after quitting smoking, with men gaining an average of 2.8 kg and women an average of 3.8 kg. Those over 55 years of age who smoke more than 15 cigarettes a day are particularly prone to weight gain after quitting.

What exactly causes this? Researchers have found that emotional and behavioral factors play a role, including the habit of putting things in one's mouth. Nicotine in tobacco accelerates overall physiological functions, especially the frequency of food metabolism, even though smoking mostly occurs during leisure time. Excessive smoking often increases heart rate; smokers' average heart rate is 84 beats per minute, compared to 72 beats per minute for non-smokers. Once smoking stops, metabolism slows down, food is consumed more slowly, and weight gain occurs.

People who quit smoking often relapse into their cravings, and when they quit, they often experience a sense of emptiness and crave sweets. This is because nicotine lowers insulin levels in the blood, thus reducing cravings for sweets. With the effects of nicotine gone, insulin levels often rise, leading people to eat more sweets.

So, does this mean smoking can be a way to lose weight? Actually, no. The harm caused by smoking far outweighs the harm caused by being overweight; a significant number of patients die from smoking-related diseases. Do Chinese people experience the same thing as Americans? Although we haven't conducted large-scale epidemiological surveys, clinical observations have revealed that many underweight patients who quit smoking experienced a significant improvement in their facial complexion, but their weight did not increase significantly. In some cases, weight gain was closely related to changes in dietary habits.

**2. Sleep and Obesity**

Scientific research has found a close link between sleep and obesity.

(1) Sleeping immediately after eating can easily lead to weight gain.

Medical research has found that eating and then immediately sleeping can lead to obesity. This is because, under the influence of the parasympathetic nervous system, fat is easily stored in the body at night. When the body is awake, the sympathetic nervous system is extremely active, but once asleep, the parasympathetic nervous system takes over, making it easier for fat to accumulate.

Furthermore, calorie consumption drops to a minimum during sleep, and unburned calories are stored as fat. People who eat and then sleep are generally more prone to weight gain. This is similar to how Japanese sumo wrestlers, when trying to gain weight, often eat large meals and then immediately go to sleep; or they eat a large meal before bed and then swallow it whole, which over time leads to obesity.

Eating before bed not only leads to weight gain but also disrupts sleep. Your stomach has to work hard to digest the food you eat, and this stimulation is transmitted to the brain, causing restless sleep. As a result, your lifestyle becomes increasingly irregular.

(2) Lack of sleep can lead to weight gain.

A US study indicates that insufficient sleep may affect the secretion of hormones that help burn calories during the day, thus leading to obesity.

Researchers tracked approximately 500 adults aged 27 to 40 for 13 years and found that during this period, women's average nightly sleep time decreased from 7.7 hours to 7.3 hours, while men's decreased from 7.1 hours to 6.9 hours. During the same period, these individuals gained an average of 5 pounds. Those who slept less than 6 hours per night experienced the greatest weight gain.

Dr. Hassler, who led the study, believes that a key factor contributing to this phenomenon is that the longer a person stays up late, the more free time they have to eat.

Harvard Medical School sleep expert Patel also stated that various chemicals and hormones have been proven to play a role in controlling appetite and increasing weight. If sleep time increases or decreases by one or two hours, the secretion of related chemicals and hormones in the body will change.

Robert D. Vorona and his colleagues at the Eastern Virginia Medical School also conducted an experiment, interviewing 924 participants aged 18 to 91 who completed questionnaires on topics such as demographics, medical issues, sleep habits, and sleep disorders.

The results showed that total sleep time decreased with increasing BMI. The difference in sleep time between people of normal weight and others was 16 minutes per day, totaling 2 hours per week. The results remained similar after researchers excluded specific sleep disorders (such as obstructive sleep apnea) and insomnia.

Based on this finding, Vorona points out that reduced sleep may affect metabolism and hormones. For example, limited sleep may reduce leptin levels (a hormone related to appetite regulation), thus affecting the relationship between sleep and obesity. Or it may simply be related to increased meal times. Although they caution that this study did not establish a causal relationship between limited sleep and obesity, it does "suggest that sleeping an extra 20 minutes per night appears to be associated with a lower BMI."