IronNEW2026-08

Effects of the Mediterranean Diet, Ketogenic Diet, and Intermittent Fasting on Iron Metabolism and Iron Deficiency Risk in Adults with Obesity: A Systematic Literature Review.

La Vignera Sandro, Condorelli Rosita — Nutrients

Summary

This review explored how three popular diets—Mediterranean, ketogenic, and intermittent fasting—affect iron levels in adults with obesity. It found that the Mediterranean diet seems most protective for iron status, while ketogenic diets might increase the risk of iron deficiency. Overall, losing weight generally helps improve iron levels by reducing inflammation.

AI-generated summary — read the original

Key points

The Mediterranean diet appears most beneficial for maintaining healthy iron levels in people with obesity.
Ketogenic diets might increase the risk of iron deficiency due to limited food choices and potential absorption issues.
Intermittent fasting has varied effects on iron markers, but weight loss itself consistently improves iron status.
Monitoring iron levels is important for individuals with obesity undertaking any dietary intervention.

What the study looked at

This systematic review investigated how three popular dietary patterns—the Mediterranean diet, ketogenic diet, and intermittent fasting—influence iron metabolism and the risk of iron deficiency in adults living with obesity. Researchers conducted a comprehensive search across several scientific databases, analyzing existing studies that examined the effects of these diets on iron status in obese individuals. They carefully screened hundreds of papers to include only the most relevant and high-quality research. The review concluded that the Mediterranean diet appeared to be the most beneficial for maintaining healthy iron levels, likely due to its anti-inflammatory components and variety of iron-rich foods. In contrast, ketogenic diets were identified as potentially increasing the risk of iron deficiency, possibly by restricting diverse iron sources and affecting absorption. Intermittent fasting showed more complex and varied effects on iron markers, but a consistent finding was that weight loss itself generally improved iron status by reducing chronic inflammation often associated with obesity.

Dietary takeaway

To support healthy iron levels, especially if you have obesity, consider a balanced eating pattern like the Mediterranean diet, which offers diverse nutrient-rich foods. Be mindful that highly restrictive diets, such as ketogenic diets, might limit your intake of various iron sources and could potentially impact absorption. Remember, this is a review of existing studies, and individual dietary needs vary, so consult a healthcare professional for personalized advice.

Abstract

BACKGROUND/OBJECTIVES: Obesity is paradoxically associated with iron deficiency despite adequate dietary intake, driven by chronic inflammation and elevated hepcidin. Different dietary patterns may differentially affect iron metabolism in obese individuals, yet comparative evidence remains limited. METHODS: We conducted a systematic literature review following PRISMA 2020 guidelines. Four databases (SciSpace, Google Scholar, PubMed) were searched through 2025 using terms related to obesity, iron deficiency, and three dietary patterns: Mediterranean diet, ketogenic diet, and intermittent fasting. Studies were screened using seven predefined criteria (three inclusion, four exclusion) with thresholds of ≥4.0/5.0 for abstract screening and ≥4.5/5.0 for full-text screening. RESULTS: From 396 identified records (SciSpace = 325, Google Scholar = 57, PubMed = 14), 38 studies were included after removing 62 duplicates and screening 334 unique records. Studies without accessible full text were excluded.The Mediterranean diet appears most protective for iron status due to its anti-inflammatory profile (omega-3 fatty acids, polyphenols, vitamin C) and bioavailable iron sources. Ketogenic diets may impair duodenal iron absorption through hepcidin-independent mechanisms and restrict dietary iron diversity. Intermittent fasting shows complex effects, remodeling iron metabolism with increased transferrin and decreased ferritin within physiological ranges. Weight loss per se consistently improves iron status by reducing adipose-driven inflammation and lowering hepcidin. CONCLUSIONS: Among the three dietary patterns examined, the Mediterranean diet appears most protective for iron status in obese individuals. The ketogenic diet may pose the highest risk due to restricted dietary iron diversity and potential hepcidin-independent absorption impairment. Direct comparative randomized controlled trials are urgently needed. Clinicians should routinely monitor iron biomarkers, including hepcidin, in obese patients undertaking any dietary intervention. Quantitative biomarker data from the 38 included studies showed serum ferritin reductions of 8-28%, hemoglobin levels remaining within clinically stable ranges, and IL-6 decreases of 15-42% across dietary patterns.

View on PubMed →DOI: 10.3390/nu18162681