Linoleic acid (LA), the predominant omega-6 polyunsaturated fatty acid in human diets, has been associated with improved lipid metabolism and insulin sensitivity compared with saturated fats. However, its role in metabolic health remains debated due to the limited number of well-controlled intervention studies.
This randomized controlled trial aims to evaluate the metabolic effects of an LA-rich oil compared with a blended oil in adults with insulin resistance. Participants will be randomly assigned to receive either a daily supplement of LA-rich oil or a control blend oil for 8 weeks, while maintaining their usual diet and lifestyle. The primary outcome is the change in insulin resistance, assessed by the Homeostatic Model Assessment of Insulin Resistance (HOMA-IR). Secondary outcomes include changes in fasting glucose, insulin, lipid profile, inflammatory and oxidative stress markers, and body composition.
The study is designed as a single-blind, parallel-group intervention conducted at the Pontifical Catholic University of Chile. The results are expected to clarify the effects of increased dietary linoleic acid intake on insulin sensitivity and metabolic risk factors, contributing to the ongoing debate about the role of omega-6 fatty acids in cardiometabolic health.
Men and women aged 20 to 60 years.
Insulin resistance (HOMA-IR > 2.6).
At least one cardiometabolic risk factor: abdominal obesity (waist circumference > 90 cm in men or > 80 cm in women); low HDL-cholesterol (< 40 mg/dL in men or < 50 mg/dL in women); elevated LDL-cholesterol (> 70 / 100 / 130 mg/dL, according to estimated cardiovascular risk); or elevated blood pressure (≥ 130/85 mmHg).
Diabetes diagnosis.
Severe psychiatric illness.
Malabsorption disorders or previous bariatric surgery.
Pregnancy or lactation.
Parallel
Linoleic Acid-Rich Oil
Dietary supplementParticipants in the experimental group will receive a daily supplement of a linoleic acid (LA)-rich oil at a dose of 0.4 mL per kilogram of body weight per day, taken orally for 8 weeks. The oil is characterized by a high content of omega-6 polyunsaturated fatty acids, primarily linoleic acid (\~60%). To facilitate adherence and appropriate use, participants will receive a recipe booklet encouraging the use of the oil in cold or minimally cooked preparations, or as a topping over foods. They will be instructed to avoid prolonged heating and to store the oil protected from light and at room temperature. The supplement will be provided in identical coded bottles to maintain single-blind conditions. Participants will be asked to maintain their usual diet and lifestyle throughout the intervention.
Blend Oil
Dietary supplementParticipants in the control group will receive a daily supplement of a blend oil at a dose of 0.4 mL per kilogram of body weight per day, taken orally for 8 weeks. The blend was formulated to contain approximately equal proportions of saturated, monounsaturated, and polyunsaturated fatty acids, with less than half the linoleic acid content of the LA-rich oil. Participants will receive a recipe booklet promoting the use of the oil in cold dishes or lightly cooked preparations, or as a dressing or drizzle over meals. They will also be instructed on proper storage away from heat and direct light. The supplement will be supplied in identical coded bottles to ensure blinding. Participants will maintain their usual diet and lifestyle during the intervention.
Change in insulin resistance (HOMA-IR)
Insulin resistance will be assessed using the Homeostatic Model Assessment of Insulin Resistance (HOMA-IR), calculated from fasting glucose and fasting insulin concentrations. The primary outcome is the change in HOMA-IR from baseline to week 8 between the two study groups.
Glycated hemoglobin (HbA1c)
HbA1c (%) will be measured to assess glucose homeostasis.
Fasting glucose
Fasting glucose (mg/dL) will be measured to assess glucose homeostasis.
Fasting insulin
Fasting insulin (µU/mL) will be measured to assess glucose homeostasis.
Lipid profile
Plasma concentrations (mg/dL) of total cholesterol, HDL-cholesterol, LDL-cholesterol, and triglycerides will be determined using standard enzymatic assays.
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