Researchers studied 512 people with obesity who followed a special diet using meal replacement shakes for 12 weeks. They discovered that people with a specific genetic variation (a tiny difference in their DNA) lost significantly more weight and improved their heart health markers better than others on the same diet. People without the G version of this gene lost about 9 pounds and improved their cholesterol and blood sugar more dramatically. This suggests that your genes might play a role in how effective a diet plan will be for you personally.

The Quick Take

  • What they studied: Whether a specific genetic variation affects how much weight people lose and how much their heart health improves when following a meal replacement diet
  • Who participated: 512 adults of European descent who were severely obese (BMI over 35), meaning they were significantly overweight according to medical standards
  • Key finding: People without the G genetic variant lost about 9 pounds and improved their blood sugar and cholesterol levels much more than people with the G variant, who lost about 4 pounds on the same diet
  • What it means for you: Your genes may influence how well a meal replacement diet works for you. This doesn’t mean the diet won’t work—it just means some people may see better results than others. Talk to your doctor about whether genetic testing might help personalize your weight loss plan.

The Research Details

Scientists recruited 512 people with severe obesity and had them all follow the same diet plan for 12 weeks. The diet involved replacing some regular meals with special shakes to reduce overall calories. Before and after the diet, researchers measured everyone’s weight, body fat, waist size, blood pressure, and blood sugar levels. They also looked at each person’s DNA to identify which genetic variant they carried. The researchers then compared how much weight and health improvement each genetic group achieved.

Understanding how genes affect diet success is important because it could help doctors recommend the best diet approach for each individual person. Instead of a one-size-fits-all approach, doctors might eventually be able to predict who will benefit most from specific diets based on genetic testing.

This was a well-designed study with a large number of participants (512 people), which makes the results more reliable. All participants followed the same diet for the same length of time, which is good for comparison. However, the study only included people of European descent, so results may not apply equally to other ethnic groups. The study was completed in 12 weeks, which is a reasonable timeframe but doesn’t tell us about long-term results.

What the Results Show

People without the G genetic variant (called CC carriers) lost significantly more weight than those with at least one G variant. The CC group lost an average of 9 pounds compared to 3.8 pounds in the G-carrier group. Their BMI (a measure of body weight relative to height) dropped by 2.3 points versus 1.0 point in the other group. Body fat loss was also much greater: 8.1 pounds versus 2.8 pounds. Waist circumference (belly size) decreased by 6.8 centimeters in CC carriers versus 5.1 centimeters in G carriers. All of these differences were statistically significant, meaning they’re unlikely to be due to chance.

Beyond weight loss, people without the G variant also showed much better improvements in metabolic health markers. Their blood sugar dropped 15 points compared to 4 points in G carriers. Insulin levels (a hormone that controls blood sugar) decreased by 9.8 units versus 3.7 units. Cholesterol improvements were dramatic: total cholesterol dropped 23 points versus 9 points, and triglycerides (a type of blood fat) dropped 24 points versus 4 points. The good cholesterol (HDL) increased more in CC carriers. Inflammation markers also improved more in the CC group. Most importantly, people without the G variant had a much lower risk of developing metabolic syndrome (a cluster of conditions that increase heart disease risk) after the diet.

This is the first study to specifically examine how this particular genetic variation affects weight loss on a meal replacement diet. Previous research has shown that this gene affects how the body processes fat and glucose, but no one had tested it with this specific diet approach. The findings align with what scientists know about how this gene works in the body—it appears to influence how efficiently people can lose weight and improve their metabolic health.

The study only included people of European descent, so we don’t know if these results apply to people of other ethnic backgrounds. The study lasted only 12 weeks, so we don’t know if these differences persist over months or years. The research doesn’t explain why the genetic variation causes these differences—it just shows that it does. Additionally, all participants were severely obese, so results may not apply to people with mild or moderate obesity.

The Bottom Line

If you’re considering a meal replacement diet for weight loss, this research suggests it could be effective, but your results may vary based on your genetics. Discuss genetic testing with your doctor to see if it might help personalize your weight loss approach. Regardless of your genetic makeup, following a structured meal replacement diet under medical supervision appears beneficial for weight loss and heart health. (Confidence level: Moderate—this is one study, though well-designed)

People with obesity considering weight loss options should know about this research. Those with a family history of difficulty losing weight or metabolic problems might particularly benefit from genetic testing. Healthcare providers recommending weight loss diets should be aware that genetic factors may influence outcomes. This research is less relevant to people at a healthy weight or those with mild overweight.

In this study, significant weight loss and health improvements occurred within 12 weeks. However, this doesn’t mean you’ll see results that quickly—individual timelines vary. Most people can expect to see meaningful changes within 8-12 weeks if they stick with the diet, but some may see results sooner or take longer depending on their genetics and other factors.

Want to Apply This Research?

  • Track weekly weight, waist circumference, and energy levels. If you know your genetic status, log it in your profile to compare your progress against expected outcomes for your genetic group. Monitor blood sugar and cholesterol improvements through regular medical checkups every 4-6 weeks.
  • Use the app to log meal replacement shakes and track adherence to the diet plan. Set weekly weight loss goals (1-2 pounds per week is typical) and celebrate milestones. If you’re a G-carrier and seeing slower progress, use the app to adjust calorie targets or meal timing rather than abandoning the diet, as it’s still beneficial.
  • Create a dashboard showing weight trend, waist circumference trend, and metabolic markers (blood sugar, cholesterol) if available through health integrations. Compare your progress monthly to expected outcomes. If progress stalls, use the app to identify adherence issues or discuss with your healthcare provider whether adjustments are needed.

This research describes a scientific study and should not be interpreted as medical advice. The findings apply specifically to adults with severe obesity of European descent who followed a structured meal replacement diet. Individual results vary based on genetics, lifestyle, and other health factors. Before starting any weight loss diet or genetic testing, consult with your healthcare provider or a registered dietitian. This study does not replace professional medical evaluation or treatment recommendations. If you have metabolic syndrome, diabetes, or other health conditions, medical supervision is essential before beginning any diet program.