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Why do people gain weight after stopping smoking?
Last reviewed: 01.07.2025
Fear of gaining weight is one of the main reasons why smokers do not quit. The underlying causes of weight gain are thought to be metabolic disorders, but there has been no specific data on these disorders so far. A researcher from Austria told participants of the International Congress of Endocrinology and the European Congress of Endocrinology about her work. She found that changes in insulin synthesis may be associated with weight gain after quitting smoking.
Marietta Stadler, a doctor at the Haizing Hospital in Vienna, recruited smokers who were part of a national smoking cessation program to take part in her study. In this study, they underwent a 3-hour glucose tolerance test before they quit and at least 3 and 6 months after they had quit. Their body composition was also measured at the same time.
The scientists measured insulin production by beta cells during fasting and after glucose ingestion, and assessed the participants' appetite by offering them a snack. They also measured levels of several hormones involved in regulating metabolism and appetite.
"We found that body weight and fat mass increased by 5% and 23%, respectively, after 3 months of quitting," Dr. Stadler noted, "and by 6 months, the increases were 7% and 36%, respectively." More interesting metabolic findings included an increase in first-phase insulin secretion in response to glucose stimulation and an increase in carbohydrate intake during snacks after 3 months of quitting. Participants had significant fasting insulin resistance at 3 months but not at 6 months, while postfasting insulin sensitivity, as assessed by the glucose tolerance test, remained unchanged throughout the study. Fasting neuropeptide Y (NPY) values were elevated at 3 months but not at 6 months.
"We speculate that the changes in insulin synthesis may be related to the compulsive craving for carbohydrates and weight gain that almost all smokers experience when they quit. However, the increase in insulin secretion and carbohydrate intake appears to be a transient effect of smoking cessation, as these changes were not observed after 6 months, although the participants had gained more weight.
"All of these factors are indicators for understanding the metabolic processes that are associated with weight gain after smoking cessation," concluded Dr. Stadler. "The more we can understand the biological basis of this phenomenon, the greater our chances of controlling it."