Researchers wanted to know if being a morning person, night owl, or somewhere in between affects how much weight people lose after weight loss surgery. They studied 263 patients in Italy and measured their weight loss at 6 and 12 months after surgery. Surprisingly, they found that your natural sleep and activity schedule didn’t make a difference in how successful the surgery was. Everyone lost similar amounts of weight regardless of whether they naturally preferred mornings or evenings. This suggests that while your daily rhythm matters for health, it may not be the key factor determining weight loss surgery results.

The Quick Take

  • What they studied: Whether being a ‘morning person’ or ’night owl’ affects how much weight people lose after weight loss surgery
  • Who participated: 263 adults with severe obesity who had weight loss surgery at one hospital in Italy. Researchers checked what time of day each person naturally preferred to sleep, eat, and exercise.
  • Key finding: There was no meaningful difference in weight loss between morning people, night owls, and those in between at 6 months or 12 months after surgery. All groups lost similar amounts of weight.
  • What it means for you: If you’re considering weight loss surgery, your natural sleep schedule probably won’t determine your success. However, this was one study at one hospital, so more research is needed to confirm these findings apply to everyone.

The Research Details

This was a single-center study, meaning researchers followed patients at just one hospital in Italy. They enrolled 263 people who were having weight loss surgery and measured several things before surgery: their weight, height, body measurements, blood work, and their natural sleep and activity preferences (chronotype). The researchers categorized people into three groups based on whether they naturally preferred mornings, evenings, or were somewhere in between. After surgery, they measured the same patients again at 6 months and 12 months to see how much weight they had lost and how their body measurements changed.

Understanding what factors influence weight loss surgery success is important because it could help doctors predict who will do well after surgery and tailor their care. If chronotype mattered, doctors could potentially adjust timing of meals or activities to help patients lose more weight. This study helps clarify whether this biological rhythm factor is actually important.

This study has some strengths: it measured multiple weight loss outcomes, had a reasonable sample size of 263 people, and followed patients for a full year. However, it was conducted at only one hospital in Italy, which means the results might not apply to people in other countries or different healthcare settings. The study didn’t provide detailed information about how they measured chronotype, which is important for understanding the results.

What the Results Show

The main finding was that chronotype (whether someone is naturally a morning person, night owl, or in between) did not significantly affect weight loss after surgery. At 6 months after surgery, all three chronotype groups lost similar amounts of weight. At 12 months, this pattern continued—there were no meaningful differences between the groups. This held true whether researchers measured absolute weight loss, BMI (body mass index), or percentage of excess body weight lost. In other words, a person’s natural preference for when to sleep and eat didn’t predict how successful their weight loss surgery would be.

The researchers measured several different ways of calculating weight loss (absolute weight, BMI, percentage of initial body weight lost, and percentage of excess body weight lost) to make sure their finding was consistent. All of these measurements showed the same result: chronotype didn’t matter. This consistency across different measurement methods strengthens their conclusion.

This finding is somewhat surprising because previous research has shown that chronotype affects eating patterns, metabolism, and other health factors. Many scientists thought that night owls might have different weight loss outcomes than morning people because they tend to eat at different times and have different activity patterns. However, this study suggests that after weight loss surgery, these differences in daily rhythm may not be as important as other factors in determining weight loss success.

This study was conducted at only one hospital in Italy, so results might not apply to people in other countries or healthcare systems. The study didn’t provide detailed information about how chronotype was measured, which makes it harder to understand exactly what was being studied. The researchers also noted that more detailed information about each person’s daily schedule and eating patterns could have provided clearer answers. Additionally, this study only looked at people with severe obesity, so results might differ for people with less severe weight issues.

The Bottom Line

If you’re considering weight loss surgery, don’t worry about whether you’re a morning person or night owl—it probably won’t affect your results. Focus instead on following your doctor’s post-surgery instructions about diet, physical activity, and follow-up appointments, as these are proven to matter. (Moderate confidence: based on one study at one location)

This information is relevant for anyone considering weight loss surgery who might be concerned about their natural sleep schedule affecting outcomes. It’s also useful for doctors and surgeons counseling patients about what to expect. However, this study only included people with severe obesity, so results might be different for people with less severe weight concerns.

Weight loss after surgery happens gradually. Most significant weight loss occurs in the first 6 months, with continued gradual loss through 12 months. Don’t expect overnight results, but consistent progress should be visible within the first few months if you follow post-surgery guidelines.

Want to Apply This Research?

  • Track your weight weekly and calculate your percentage of weight lost monthly. Also note your daily eating times and activity times to see your personal patterns, even though chronotype may not affect overall results.
  • Use the app to set reminders for meals at consistent times (regardless of whether you’re a morning or evening person) and track your physical activity. Focus on consistency rather than timing of day.
  • Monitor weight trends over 4-week periods rather than daily fluctuations. Track adherence to post-surgery dietary guidelines and activity goals, as these appear to be more important than the time of day you naturally prefer to be active.

This research suggests that your natural sleep and activity preferences may not significantly affect weight loss surgery outcomes, but this finding comes from one study at one hospital. Individual results vary, and many other factors affect weight loss surgery success. Always consult with your bariatric surgeon or healthcare provider about your specific situation, expected outcomes, and post-surgery care plan. This information is for educational purposes and should not replace professional medical advice.