Scientists studied two groups of people who lost weight through diet and exercise changes. They wanted to know if the health improvements came from losing fat or from changing where fat sits on the body. Surprisingly, they found that people’s hearts and blood sugar got healthier after weight loss, but this improvement didn’t depend on how much fat they lost or where that fat came from. This means the benefits of weight loss might come from something else entirely—possibly just moving your body more or eating better foods, regardless of the exact numbers on the scale.

The Quick Take

  • What they studied: Whether the health improvements from weight loss come from losing fat specifically or from changes in where fat is stored on your body
  • Who participated: Two separate groups: one with people who had obesity and type 2 diabetes (followed for 1 year), and another with people who were overweight without diabetes (followed for 12 weeks). Both groups made lifestyle changes or followed a diet plan.
  • Key finding: People’s insulin sensitivity (how well their body uses blood sugar) improved by about 50%, and their blood sugar control improved by about 26%, but these improvements had nothing to do with how much fat they lost or where on their body the fat came from.
  • What it means for you: The good news is that when you lose weight through diet and exercise, your heart and blood sugar health improve regardless of whether you’re losing mostly fat or a mix of fat and muscle. This suggests the real benefit comes from the lifestyle changes themselves, not just the numbers on the scale. However, talk to your doctor before starting any weight loss program, especially if you have diabetes.

The Research Details

Researchers looked at two separate studies where people made changes to their diet and activity levels. In the first study, people with obesity and diabetes were followed for a full year. In the second study, people who were overweight (without diabetes) followed a strict calorie-controlled diet for 12 weeks. The scientists used special machines (called DXA scanners and CT scans) to measure exactly how much fat people had and where it was located on their bodies—like whether it was around the belly or spread throughout the body. They also tested how well people’s bodies could handle blood sugar and measured things like cholesterol and blood pressure.

By using these precise measurement tools, the researchers could separate the effects of losing weight from the effects of changing body composition or fat distribution. This is important because previous research sometimes confused these different changes. By carefully adjusting their math to account for weight loss separately, they could see what was really driving the health improvements.

This study is fairly strong because it used objective measurements (machines to measure fat, not just scales) and tested multiple health markers. However, the sample sizes aren’t specified in the abstract, which makes it harder to judge how confident we should be in the results. The study was published in a peer-reviewed journal, meaning other experts reviewed it before publication. The fact that results were similar in two different groups (one with diabetes, one without) adds confidence to the findings.

What the Results Show

When people lost weight, their bodies showed impressive improvements in handling blood sugar. In the first group (people with diabetes), insulin sensitivity—which is how well the body uses insulin to control blood sugar—improved by about 50%. In both groups, a measure called HOMA-IR (which shows how resistant the body is to insulin) dropped by about 26%. These are substantial improvements that usually mean a lower risk of heart disease and better diabetes control.

Interestingly, when the researchers looked at whether these improvements were connected to changes in body fat percentage or where the fat was located, they found no connection. In other words, people whose fat distribution changed a lot had similar health improvements to people whose fat distribution barely changed. The same was true for body fat percentage—whether someone lost mostly fat or a mix of fat and other tissue, their health markers improved similarly.

This finding was consistent across both studies, which strengthens the conclusion. People in the first study lost about 9.8% of their body weight, with about 64% of that being fat. People in the second study lost about 5.3% of their body weight, with about 77% being fat. Despite these differences, the health improvements were comparable.

The study also measured other important health markers like glucose levels, cholesterol, and blood pressure, though the abstract doesn’t provide specific numbers for these. The fact that multiple health measures improved suggests the benefits of weight loss are broad and affect several body systems, not just one area.

Previous research has sometimes suggested that where you carry fat matters a lot for health—that belly fat is worse than fat elsewhere. This study suggests that while fat distribution might matter for some things, the overall health improvements from weight loss don’t depend on changing where fat is stored. This is somewhat surprising and suggests that the act of losing weight itself, through better eating and more movement, triggers health improvements through mechanisms we don’t fully understand yet.

The abstract doesn’t tell us how many people participated in each study, which makes it hard to know how confident we should be in the results. We also don’t know details about who dropped out or whether the groups were similar at the start. The studies were relatively short (12 weeks to 1 year), so we don’t know if these benefits last longer. Additionally, we don’t know if the results would be the same for people of different ages, races, or with different health conditions. The study only looked at people who successfully lost weight, so we don’t know what happens if weight loss attempts fail.

The Bottom Line

If you’re trying to improve your heart health or blood sugar control, focus on losing weight through a combination of eating better and moving more. You don’t need to obsess over whether you’re losing fat versus muscle or where the fat comes from—the health benefits appear to come from the overall lifestyle changes. Moderate confidence: This is based on two studies with similar findings, but larger studies would strengthen this conclusion.

This is especially relevant for people with type 2 diabetes or those at risk for heart disease who are trying to decide whether weight loss is worth the effort. It’s also good news for people who feel discouraged because their body shape isn’t changing as much as they expected—the health benefits are still happening. People should NOT use this as an excuse to ignore overall fitness or muscle health, as those matter for other reasons. Anyone with diabetes or heart disease should work with their doctor before making major diet or exercise changes.

The studies showed improvements within 12 weeks to 1 year, so you might expect to see some health improvements relatively quickly after starting lifestyle changes. However, the most significant improvements appeared in the longer study (1 year), suggesting that sticking with changes over time produces better results. Talk to your doctor about realistic timelines for your specific situation.

Want to Apply This Research?

  • Track weekly weight loss percentage (not just pounds) and note energy levels, how clothes fit, and any changes in hunger or cravings. This helps you see progress beyond the scale and stay motivated even when weight loss slows down.
  • Instead of obsessing over body composition changes, use the app to track two simple behaviors: daily steps or activity minutes, and meals that include vegetables and protein. These are the actual lifestyle changes that drive the health improvements, not the body measurements.
  • Set monthly check-ins to review trends in weight loss, activity levels, and how you feel overall. If you have diabetes or prediabetes, ask your doctor to check your blood sugar markers every 3 months to see if they’re improving, even if weight loss is slower than expected. This gives you concrete evidence that the lifestyle changes are working, even if the scale isn’t moving as fast as you’d like.

This research suggests that weight loss improves heart and blood sugar health through mechanisms beyond just changing body fat percentage or distribution. However, this study does not replace personalized medical advice. If you have diabetes, heart disease, or other health conditions, consult your doctor before making significant diet or exercise changes. Weight loss should be pursued safely and sustainably, ideally under professional guidance. Individual results vary, and this research may not apply to everyone. Always work with your healthcare provider to develop a plan appropriate for your specific situation.