Does olive oil help with weight loss?

Slightly, and only as part of a diet. A meta-analysis of 11 randomized trials lasting at least 12 weeks found that diets enriched in olive oil took off 2 lb (0.92 kg) more than control diets, with an interval from 1.5 to 2.6 lb (0.67 to 1.16 kg). The control diets varied, and the abstract gives no quality rating. The benefit appeared when people ate the oil as food. It did not appear when they took olive oil capsules.

Unsettled. The size of the effect is small and the comparison is loose. Every trial on this page tested olive oil inside a diet or against other fats. We found no trial of olive oil alone, added to a free diet, with weight loss as the main outcome.

What the trials found

Olive oil diets against control diets

The 11-trial meta-analysis is the strongest direct answer, and it is modest. A loss of 2 lb (0.92 kg) more than the comparison diet over three months or longer is real on the numbers and hard to notice on a scale. We read the English abstract only, because the full paper is in Spanish.

Olive oil against other oils

A meta-analysis of 52 trial articles comparing olive oil with other oils found that olive oil does not seem to change where the body stores fat. Used in cooking, it went with 0.71 lb (0.32 kg) less fat mass, with an interval from 2 lb (0.90 kg) less to 0.57 lb (0.26 kg) more. In capsules, it went with 0.62 lb (0.28 kg) more, with an interval from 0.6 lb (0.27 kg) less to 1.8 lb (0.83 kg) more. Neither result reached statistical significance. The comparison here is other oils, so this tells you about swapping one fat for another, and not about adding oil to your plate.

Five years of eating freely

PREDIMED gave 7447 older Spanish adults with type 2 diabetes or several heart risk factors a Mediterranean diet with extra virgin olive oil, a version with nuts, or a low-fat control diet, with no calorie limit. After about five years the olive oil group weighed 0.9 lb (0.41 kg) less than the control group, an interval from 1.8 lb (0.83 kg) less to 0.02 lb (0.01 kg) more, and the difference did not reach significance. This is the republished 2019 analysis, because the 2016 weight report was retracted. Olive oil came with a whole diet, and olive oil producers paid part of the cost.

Myth. The worry that a high-fat diet built on olive oil makes you gain weight did not hold up. PREDIMED found no significant difference in body weight over five years against the low-fat diet, and some evidence of less gain around the waist.

People with fatty liver

In 7 randomized trials of 529 people with nonalcoholic fatty liver disease, average BMI 32.45, olive oil lowered BMI by 0.57 kg/m2 against other diets or placebo over a median of 12 weeks. The interval ran from 1.08 to 0.06, and the trials disagreed with each other moderately. Waist size fell by 0.09 in (0.23 cm), which was not significant. These are people with a liver disease, so the result does not transfer to everyone.

What happens in everyday life

In three US cohorts of 121,119 adults followed for up to 24 years, each extra half tablespoon, 7 g, of olive oil a day went with 0.2 lb (0.09 kg) less weight gain over four years, with an interval from 0.18 to 0.24 lb (0.08 to 0.11 kg). That is weight gain avoided, and it is observational. The link weakened once overall diet quality was taken into account, and the average intake was only 3 to 4 g a day. In the same cohorts, more butter, margarine or other vegetable oils went with weight gain, and putting olive oil in their place went with less gain.

Who should be careful

Not for everyone. Olive oil is dense in energy. US survey coding counts a tablespoon as 14 g and about 126 calories, from 900 calories per 3.5 oz (100 g). Pouring it on top of what you already eat adds calories, and none of the trials above tested that.

Capsules are the other caution. The 11-trial review saw no benefit from them, and the 52-article review saw a small sign, short of significance, that they went with more fat mass. This search found no toxicity or drug interaction concern for olive oil used in cooking.

What expert bodies say

We found no agency position on olive oil and body weight. The nearest is the FDA qualified health claim for oils high in oleic acid, such as olive oil, issued on 19 November 2018. It is about heart disease, it rates the evidence supportive and not conclusive, and it attaches a condition that applies to weight as well. According to FDA, these oils should replace fats higher in saturated fat and should not increase the total calories you eat in a day. The claim names about 1.5 tablespoons, 20 g, a day.

How we searched

What would change this answer

• A meta-analysis with a formal quality rating of trials that swap olive oil for other fats at equal calories, with weight as the outcome.
• The 2024 network meta-analysis of edible oils, once someone checks what it says about olive oil.
• A randomized trial of olive oil alone with weight loss as the main outcome. We found none registered.

Its nutrients, fat profile and cooking numbers are on the olive oil page.

Sources

1. ev-oowl-01 · Meta-analysis or systematic review · systematic review and meta-analysis of RCTs, search to December 2016 · n = 11 RCTs
   A diet enriched in olive oil reduced weight more than control diet: -0.92 kg, 95% CI (-1.16, -0.67), p heterogeneity = 0.1; decreased waist circumference in -0.60 cm, 95% CI (-1.17, -0.04), p heterogeneity = 0.6; and diminished BMI in -0.90, 95% CI (-0.91, -0.88), p heterogeneity < 0.001. The benefits were seen when olive oil was supplemented in its natural state and not when capsules were given.
   
   Who: adults without previous cardiovascular events, RCTs of at least 12 weeks
   Effect: weight -2 lb (95% CI -2.6 to -1.5; metric: -0.92 kg, -1.16 to -0.67); waist -0.24 in (-0.46 to -0.02; metric: -0.60 cm, -1.17 to -0.04); BMI -0.90 (-0.91 to -0.88)
   Certainty: Small effect; control diets varied; Spanish-language journal, full text not read, English abstract used. No GRADE rating in abstract. The BMI interval (-0.91 to -0.88) is implausibly narrow and is not used.
   Rev Esp Salud Publica, 2018 · checked 2026-10-07 · we read the abstract
2. ev-oowl-02 · Meta-analysis or systematic review · systematic review and meta-analysis of RCTs, PROSPERO CRD42021234652 · n = 52 articles
   The results indicate that the consumption of olive oil does not seem to alter the distribution of body fat, despite a small indication that supplementation in capsules can increase adipose mass (Mean Difference = 0.28 kg, 95% CI [-0.27, 0.83]; between-groups difference p = 0.59) and waist circumference (mean difference = 1.74 kg, 95% CI [0.86, 1.62]; between-groups difference p < 0.01) and decrease its auxiliary culinary use (mean difference = -0.32 kg, 95% CI [-0.90, 0.26]).
   
   Who: adults in RCTs comparing olive oil with other oils
   Effect: capsules: fat mass MD +0.62 lb (95% CI -0.6 to 1.8; metric: 0.28 kg, -0.27 to 0.83), waist MD +1.74; culinary use: MD -0.71 lb (-2 to 0.57; metric: -0.32 kg, -0.90 to 0.26)
   Certainty: Comparator is other oils, not no oil; waist unit printed as kg in the abstract; confounders not explored per authors. Full text not in PMC.
   Food Funct, 2023 · checked 2026-10-07 · we read the abstract
3. ev-oowl-03 · Meta-analysis or systematic review · systematic review and meta-analysis of RCTs · n = 529
   Taking into account all included studies, a statistically significant reduction in BMI (BMI kg/m2: MD = −0.57, 95% CI: −1.08 to −0.06, p = 0.03, I2 = 51%) was observed (Figure 11). Although there was no statistically significant change in WC, there was a noticeable downward trend, as evidenced in three of the six studies (WC cm: MD = −0.23, 95% CI: −1.23 to 0.76, p = 0.65, I2 = 0%)
   
   Who: people with nonalcoholic fatty liver disease, mean BMI 32.45, median 12 weeks
   Effect: BMI MD -0.57 kg/m2 (95% CI -1.08 to -0.06), I2 51%; waist MD -0.09 in (-0.48 to 0.3; metric: -0.23 cm, -1.23 to 0.76)
   Certainty: Small trials, comparators varied; no GRADE rating for BMI in the paper.
   Nutrients, 2024, 16(6):857, The Effects of Olive Oil Consumption on Biochemical Parameters and Body Mass Index of People with Nonalcoholic Fatty Liver Disease · checked 2026-10-07 · we read the fulltext
4. ev-oowl-04 · Randomized controlled trial(s) · multicentre randomized controlled trial, reanalysed after protocol deviations · n = 7447
   After multivariable adjustment, including adjustment for propensity scores and use of robust variance estimators, the difference in 5 year changes in bodyweight in the Mediterranean diet with olive oil group was -0·410 kg (95% CI -0·830 to 0·010; p=0·056) and in the nut group was -0·016 kg (-0·453 to 0·421; p=0·942), compared with the control group.
   
   Who: men 55-80 and women 60-80 years with type 2 diabetes or three or more cardiovascular risk factors, no calorie restriction
   Effect: 5-year weight difference -0.9 lb (95% CI -1.8 to 0.02; metric: -0.410 kg, -0.830 to 0.010), p=0.056; waist -0.18 in (-0.44 to 0.07; metric: -0.466 cm, -1.109 to 0.176)
   Certainty: Republished 2019 analysis; the 2016 report (27283479) was retracted. Olive oil came with a whole Mediterranean diet, so effect is not olive oil alone. Funding partly from olive oil producers.
   Lancet Diabetes Endocrinol, 2019 · checked 2026-10-07 · we read the abstract
5. ev-oowl-05 · Randomized controlled trial(s) · multicentre randomized controlled trial · n = 7447
   A long-term intervention with an unrestricted-calorie, high-vegetable-fat Mediterranean diet was associated with no significant difference in bodyweight and some evidence of less gain in central adiposity compared with a control diet.
   
   Who: older Spanish adults at high cardiovascular risk
   Effect: no significant difference in bodyweight; some evidence of less gain in central adiposity
   Certainty: Answers the fear that adding fat makes people gain weight; does not show olive oil causes loss.
   Lancet Diabetes Endocrinol, 2019 · checked 2026-10-07 · we read the abstract
6. ev-oowl-06 · Observational data · three prospective cohorts, pooled · n = 121,119
   An increase of ½ tablespoon (7 g) servings per day of olive oil was inversely associated with body weight (multivariable-adjusted model: –0.09 kg; 95% CI: –0.11, –0.08 kg) after adjusting for sociodemographic and dietary variables at baseline and 4-y changes in the pooled analysis of the 3 cohorts.
   
   Who: Nurses' Health Study, NHSII and Health Professionals Follow-up Study, aged 65 or younger, free of chronic disease
   Effect: beta -0.09 kg per 7 g/day increase (95% CI -0.11 to -0.08) per 4-year period
   Certainty: Observational; attenuated when adjusted for overall diet quality (AHEI). Average intake was only 3-4 g a day.
   Am J Clin Nutr, 2025 · checked 2026-10-07 · we read the fulltext
7. ev-oowl-07 · Observational data · three prospective cohorts, substitution analysis · n = 121,119
   In substitution analyses, replacing margarine, butter, and other vegetable oils with equal amounts of olive oil was associated with less weight gain.
   
   Who: US adults in NHS, NHSII and HPFS
   Effect: other added fats positively associated with weight change; substitution with olive oil associated with less weight gain
   Certainty: Observational substitution model, not a trial.
   Am J Clin Nutr, 2025 · checked 2026-10-07 · we read the abstract
8. ev-oowl-08 · Position of an expert body · qualified health claim, letter of enforcement discretion, 19 November 2018 · n = —
   To achieve this possible benefit, oleic acid-containing oils should replace fats and oils higher in saturated fat and not increase the total number of calories you eat in a day.
   
   Who: US food labeling, oils with at least 70% oleic acid
   Effect: about 1.5 tablespoons (20 g) a day; benefit conditional on not increasing total calories
   Certainty: Heart claim, not a weight claim; FDA rates the evidence supportive but not conclusive.
   US FDA, Constituent Update: FDA Completes Review of Qualified Health Claim Petition for Oleic Acid and the Risk of Coronary Heart Disease, 19 November 2018 · checked 2026-10-07 · we read the section
9. ev-oowl-09 · Position of an expert body · USDA reference dataset · n = —
   FNDDS 82104000 Olive oil (fdc_id 2710186): Energy 900 kcal per 100 g; 1 tablespoon 14 g (126.0 kcal); 1 cup 224 g
   
   Who: USDA FNDDS food code 82104000, Olive oil (fdc_id 2710186)
   Effect: 900 calories per 3.5 oz (100 g); 1 tablespoon 14 g = 126 calories; 1 cup 224 g
   Certainty: calories per tablespoon calculated from 900 calories per 3.5 oz (100 g).
   USDA FNDDS 2021-2023 (FoodData Central) · checked 2026-10-07 · we read the dataset