Why does the Mediterranean diet lead to dramatic metabolic improvements for some people but only modest changes for others? A new randomized feeding trial suggests part of the answer may lie in a single post-meal blood marker.
In research published in Life Metabolism, scientists from Ruijin Hospital at Shanghai Jiao Tong University found that levels of a protein called SPARC measured one hour after a glucose drink helped predict who would benefit most from six months on a calorie-restricted Mediterranean diet. SPARC is involved in inflammation in fat tissue, and higher levels are generally associated with metabolic stress.
Researchers randomly assigned 235 adults with overweight or obesity and prediabetes to one of three calorie-restricted meal plans for six months. One group followed a Mediterranean diet, built around vegetables, whole grains, legumes, nuts, olive oil and limited red meat. A second group followed the traditional Jiangnan diet, a regional Chinese eating pattern centered on vegetables, soy foods, rice, fish and lighter cooking methods. The third group ate a contemporary Shanghai diet, reflecting typical modern urban eating habits with more refined grains, higher-fat meats and mixed cooking styles. All meals were calorie-matched and provided five days per week.
Only one measure stood out. People with lower baseline SPARC levels at the one-hour mark saw the largest improvements in insulin resistance, fasting insulin and fasting glucose while following the Mediterranean pattern. Fasting SPARC and two-hour SPARC levels did not show the same predictive value, and the one-hour relationship did not appear in the Jiangnan or control diet groups. That suggests the effect may be specific to how the Mediterranean diet interacts with certain inflammatory pathways.
The investigators also linked SPARC to changes in lipid profiles, including reductions in metabolites often associated with red-meat intake and metabolic inflammation. These shifts were most pronounced in participants following the Mediterranean diet and may help explain why the biomarker worked as a selective predictor in that group.
The study highlights an emerging theme in precision nutrition: the most useful indicators may differ depending on the eating pattern. While one-hour SPARC predicted improvements in the Mediterranean group, fasting SPARC was more relevant for people following the Jiangnan diet. The authors emphasize that no single biomarker is universally informative and that diet-specific physiology matters.
The findings underscore that biological differences can shape how each person responds to the same diet. The Mediterranean pattern remains one of the most consistently supported options for improving metabolic health, but individual variability is real and measurable.
More research is needed to determine whether SPARC or similar biomarkers could eventually help clinicians tailor dietary advice for people at higher risk for metabolic disease.
This study was supported by research grants from the National Natural Science Foundation of China, the National Key Research and Development Program of China and several Shanghai municipal science and education programs.