Short answer: Weight loss injections and aerobic endurance both lower appetite in the same part of the brain. Both bring weight down. The difference is what happens after you stop. One year after stopping semaglutide, two-thirds of the lost weight came back. In one trial, people who stopped a supervised exercise programme kept most of their weight off.
In this article
- Injections copy the fullness hormone GLP-1. Aerobic endurance makes the body change its own hunger hormones.
- Both act on the hunger centre of the brain, the hypothalamus.
- One year after stopping semaglutide, two-thirds of the lost weight came back.
- After stopping, people regained 9.6 kg after liraglutide and 3.6 kg after supervised exercise.
- For most people, start with a physician supervised exercise intervention.
How do weight loss injections lower appetite?
The new injections are a copy of a hormone the gut already makes, called GLP-1. The FDA label for semaglutide says GLP-1 helps control appetite, and its receptors sit in the parts of the brain that control hunger. The drug also slows how fast the stomach empties, and people eat less. In rat studies, semaglutide reached the hypothalamus and the brainstem, the brain’s hunger and fullness centres. Semaglutide also comes as a daily pill, approved for type 2 diabetes.
Each dose wears off. Half of a semaglutide dose is gone in about one week, so it is given once a week. Half of a liraglutide dose is gone in about 13 hours, so it is given every day. The effect lasts only as long as the doses keep coming.
How does aerobic endurance lower appetite?
Aerobic endurance means long, steady effort, such as brisk walking, easy running or cycling. During this kind of exercise the gut changes its own hormones. In 20 studies pooled together, one session lowered the hunger hormone ghrelin by about 16% and raised the fullness hormone PYY by about 9%. The body’s own GLP-1 also rose a little.
These hormones act on the same hunger centre in the brain. Ghrelin works on the hypothalamus to start hunger, and PYY works on the same area to stop it. With training, the body also gets better at feeling full after a meal. In a 12-week programme, the fullness response to a meal grew stronger.
What happens when you stop?
This is where the two roads split. In the STEP 1 trial, people lost 17.3% of their body weight on semaglutide. One year after stopping, they had gained back 11.6 points of it, about two-thirds. In the SURMOUNT-4 trial, people who stopped tirzepatide gained 14% in a year.
A trial in Copenhagen compared the two roads directly. All the people first lost 13.1 kg on a diet, then had one year of their plan, then stopped. In the year after stopping, those who had taken liraglutide gained back 9.6 kg, and those who had done supervised exercise gained back 3.6 kg. The authors say weight and body fat were maintained a year after the exercise ended.
A review of 37 studies found the same pattern. After stopping weight loss medicines, weight was predicted to be back where it started in 1.7 years. After diet and exercise programmes, it took 3.9 years. In real life, about half of people stop these medicines within a year.
What else does aerobic endurance give you?
Aerobic endurance builds a fitter heart, and fitness protects against lifestyle diseases. In 33 studies, each step up in fitness, about 1 km per hour faster running, came with 15% fewer heart events and 13% lower risk of death. The same step came with 10% lower risk of type 2 diabetes and 8% lower risk of high blood pressure. These numbers come from people followed over time, so they show a link, not proof of cause.
Who should start with injections?
Injections are the right first choice for some people. In the SELECT trial of 17,604 people with heart disease and overweight, weekly semaglutide lowered heart attacks, strokes and heart deaths from 8.0% to 6.5%. The labels also cover obesity, sleep apnoea with obesity (tirzepatide) and type 2 diabetes. Your doctor decides, case by case.
Even then, the labels say the injections are used together with a reduced calorie diet and more physical activity. Exercise is the base, and the medicine is added on top. For most people who want to lose weight and keep it off, a physician supervised exercise intervention is the place to start. At Cardiac Rehab in Film Nagar, Hyderabad, this is physician supervised, exercise based cardiac rehab, built for you and supervised every session.
Your questions, answered
Do weight loss injections stop working when you stop them?
Yes, the effect fades. The drug leaves the body, and hunger and weight come back. One year after stopping semaglutide, people in the STEP 1 trial had gained back about two-thirds of the weight they lost. That is why the labels describe these medicines as long-term treatment, used with diet and physical activity.
Does exercise really lower appetite?
Yes, for a while after each session. Aerobic exercise lowers the hunger hormone ghrelin and raises the fullness hormone PYY. Both act on the hunger centre of the brain. Over weeks of training, the body also feels full sooner after a meal. The effect builds with the habit, so it works best done regularly.
Which is better for keeping weight off, injections or exercise?
In one trial, exercise kept it off better after stopping. People regained 9.6 kg in the year after stopping liraglutide and 3.6 kg after stopping supervised exercise. While they are being taken, injections can bring weight down more. The best plan is the one you can keep up, and your doctor can help you choose.
Who should take weight loss injections first?
People with heart disease and overweight benefit most clearly. In the SELECT trial, weekly semaglutide lowered heart attacks, strokes and heart deaths from 8.0% to 6.5%. The labels also cover obesity, sleep apnoea with obesity and type 2 diabetes. Even then, they are used together with diet and physical activity.
What is a physician supervised exercise intervention?
It is exercise planned and watched over by a doctor. At Cardiac Rehab we check your heart first, set the right effort for you, and raise it step by step. Each session is supervised. It suits people who want to lose weight safely, including people with heart disease, diabetes or high blood pressure.
Start with a physician supervised exercise intervention
Thinking about weight loss injections? Ask your doctor about a physician supervised exercise intervention first. Cardiac Rehab is at Film Nagar, Jubilee Hills, Hyderabad. You can write to info@cardiacrehab.com, visit www.CardiacRehab.com, or message on WhatsApp. The endurance side is explained in Weight loss injection or endurance running: what stays? on TelanganaRunners.com.
info@cardiacrehab.com · www.CardiacRehab.com
Cardiac Rehab, 7B Journalist Colony, Film Nagar, Jubilee Hills, Hyderabad, Telangana 500096
References
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- FDA. SAXENDA (liraglutide) injection, prescribing information. dailymed.nlm.nih.gov/dailymed/search.cfm?query=saxenda
- FDA. ZEPBOUND (tirzepatide) injection, prescribing information. dailymed.nlm.nih.gov/dailymed/search.cfm?query=zepbound
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