Han Seon-hwa
The author is an honorary professor at UST and former president of the Korea Institute of Science and Technology Information.
When a new year begins, many people make fresh resolutions. Among them, one of the most common is the promise to lose weight and become healthier. For that reason, neighborhood gyms have traditionally filled with new members every January. This year, however, the situation appears somewhat different. A way to become slimmer without intense exercise or strict dieting has attracted growing attention. The change is linked to the rapid rise of new anti-obesity drugs.

The obesity medications drawing the most attention today are based on GLP-1, or glucagon-like peptide-1. GLP-1 is a natural hormone released in the intestine after eating. It stimulates insulin secretion and induces a feeling of fullness.
The human body constantly sends signals related to hunger and satiety. Hormones produced in the gut and pancreas communicate with the brain. The brain interprets those signals and determines whether a person should keep eating or stop. GLP-1–based medications strengthen the signals that indicate fullness so the brain perceives the body as already satisfied.
As a result, appetite decreases and stomach movement slows. These effects help regulate blood sugar and often lead to weight loss. In simple terms, the medication adjusts the signals reaching the brain and makes the brain believe that the body has eaten enough.
Yet, while such drugs can change appetite signals, they cannot fundamentally alter the brain's basic settings. This explains why many people experience the so-called yo-yo effect after stopping the medication.
The brain remembers repetition. When a particular behavior is repeatedly followed by a reward the brain records it as a safe choice worth repeating. That is why the feeling of satisfaction after exercise can be more powerful than simply telling oneself to exercise.
For this reason, healthy choices should begin with small and concrete actions. Something as simple as walking for 10 minutes after dinner can become the starting point. When the same action occurs repeatedly in the same situation, the brain gradually automates the behavior, allowing it to happen with less conscious effort.
Medication may temporarily alter the signals that influence the brain. But the factor that ultimately reshapes the brain is the repetition of everyday life. Rather than relying on drugs that deceive the brain, cultivating habits that guide the brain toward healthier default choices is a far more sustainable path.
This article was originally written in Korean and translated by a bilingual reporter with the help of generative AI tools. It was then edited by a native English-speaking editor. All AI-assisted translations are reviewed and refined by our newsroom.

Meanwhile : Deception and training