A landmark study showing that after weight loss, your appetite hormones shift to drive regain - and those changes are still there a year later. It's biology, not willpower.
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Long-Term Persistence of Hormonal Adaptations to Weight Loss - Sumithran et al., NEJM 2011 (PDF)
If you've lost weight and felt relentlessly hungrier afterward - for months, not days - this study explains why. It measured appetite hormones after weight loss and found the changes that drive regain were still present a full year later.
Dr. Hammer's 5 Second Takeaways
Weight loss shifts your hunger hormones toward regain
After you drop weight, hunger-promoting signals rise and fullness signals fall. Your body is quietly nudging you to eat more and rebuild what you lost.
These changes don't fade quickly
The headline finding: a year after weight loss, those hormone changes still hadn't returned to normal. The push to regain is long-lasting, not a brief adjustment that passes in a few weeks.
Hunger after weight loss is biology, not weakness
If staying at a lower weight feels like constant low-grade hunger, that's a real, measurable physiological signal - not a lack of discipline.
Put it into action: treat hunger management (protein, fiber, sleep, support) as a permanent part of maintenance, not a short-term phase you power through.
Keeping weight off needs long-term strategies
Because the biology persists, lasting results come from durable supports - not a willpower sprint that ends when the diet does.
This is a big reason regain is so common
These lasting hormonal adaptations are a key reason most people regain - and why ongoing tools (lifestyle, and sometimes medication) genuinely matter.
Nerd-Out
In 50 participants who lost weight on a 10-week very-low-energy diet, the expected appetite-hormone shifts appeared: reduced leptin, peptide YY, cholecystokinin, insulin, and amylin, with increased ghrelin, gastric inhibitory polypeptide, and pancreatic polypeptide - alongside increased subjective appetite. At 62 weeks, despite partial regain, these mediators had not reverted to baseline (leptin, PYY, CCK, insulin, and amylin remained low; ghrelin remained elevated), and hunger remained above pre-loss levels. The authors conclude that the coordinated hormonal adaptation favoring regain persists for at least a year, supporting long-term behavioral or pharmacologic strategies to counter it.
Go to the Source:
This summary is drawn from "Long-Term Persistence of Hormonal Adaptations to Weight Loss" by Sumithran and colleagues (New England Journal of Medicine, 2011; 365:1597-1604). The full paper is in the linked PDF above.