Can Post-Meal SPARC Levels Predict Success on a Mediterranean Diet?

A single postprandial biomarker may forecast Mediterranean-diet responders

identifies 1-hour postprandial SPARC as a candidate predictor of cardiometabolic response to a calorie-restricted Mediterranean diet in adults with overweight or obesity and prediabetes.

The working hypothesis behind the work is straightforward: adipose-tissue inflammation drives much of the metabolic dysregulation seen in prediabetes, and SPARC (Secreted Protein Acidic and Rich in Cysteine) is a secreted glycoprotein linked to that inflammatory milieu. If circulating SPARC reflects adipose stress, its trajectory after a glucose load could plausibly index who retains the most "metabolic room" to improve.

What the trial actually measured

• Design: Six-month randomized controlled feeding trial, 235 Chinese adults with overweight or obesity and prediabetes.
• Arms: Calorie-restricted Mediterranean diet, traditional Jiangnan diet, or a contemporary Shanghai-style control diet; all delivered with a 25% caloric deficit and controlled meals five days per week.
• Sampling: Circulating SPARC was quantified at fasting, 1 hour, and 2 hours after a glucose load.
• Outcome window: Baseline biomarker values were tested against six-month changes in insulin resistance, fasting insulin, and fasting glucose.

The investigators, led by Drs. Jiqiu Wang and Guang Ning at Ruijin Hospital, Shanghai Jiao Tong University, report that only the 1-hour post-glucose SPARC value at baseline — not fasting or 2-hour SPARC — tracked the magnitude of metabolic improvement in the Mediterranean arm. Lower baseline SPARC-1H corresponded with greater reductions in insulin resistance, fasting insulin, and fasting glucose after six months of dietary adherence under caloric restriction.

Diet-specificity matters

The predictive signal did not transfer across the other eating patterns. Neither the Jiangnan arm nor the Shanghai-style control diet showed the same SPARC-1H relationship, indicating a diet-specific metabolic interaction rather than a generic "responder" marker.

The supplementary lipidomic data reinforce that interpretation. SPARC-1H tracked closely with reductions in specific plasmalogen species — ether-linked phospholipids associated with red-meat intake and metabolic inflammation — shifts that are characteristic of Mediterranean-style eating. A separate analysis further suggests that different dietary patterns may require different predictive indicators: fasting SPARC, rather than postprandial SPARC, was associated with improvement among participants following the traditional Jiangnan diet.

Practical implications and limits

The mechanism on offer is testable: a single post-meal blood draw, taken one hour after glucose intake, could triage patients toward a Mediterranean template when SPARC-1H is low, and toward alternative strategies when it is not. That is a meaningful step beyond multi-omics panels for routine clinical use.

The verdict, however, must remain conditional. The cohort is homogeneous (Chinese adults with a defined metabolic phenotype), the feeding is controlled rather than free-living, and the comparator diets share the same caloric deficit — meaning SPARC-1H is currently a predictor of Mediterranean-specific incremental benefit, not weight loss itself. Independent replication in diverse populations, and trials without matched caloric restriction, are required before the marker enters any guideline.