Does a low-fat diet lower cholesterol?

Slightly. A 2020 Cochrane review of 37 randomized trials in 57,079 adults who were not trying to lose weight found that eating less fat lowered LDL cholesterol by 0.13 mmol/L, about 5 mg/dL, and total cholesterol by 8.9 mg/dL (0.23 mmol/L). Part of that drop came with the 3.1 lb (1.4 kg) of weight people lost. HDL cholesterol and triglycerides barely moved. The larger effects in the older literature follow how much saturated fat was cut, not how much fat in total.

Established. Across several meta-analyses of randomized trials, low-fat diets lower LDL cholesterol by a small amount, between 3.11 and 4.41 mg/dL against high-fat diets in trials of overweight adults. That is real and it is modest.

What the trials found

Total fat moves cholesterol a little

Three syntheses point the same way. The Cochrane review found the 0.13 mmol/L LDL fall above. A meta-analysis of 32 trials lasting at least a year found LDL 3.11 mg/dL lower on low-fat diets (95% CI 1.71 to 4.51) and total cholesterol 4.55 mg/dL lower. A 2018 meta-analysis of 20 trials in 2,106 people with overweight or obesity found LDL 4.41 mg/dL lower and total cholesterol 7.05 mg/dL lower.

In the 32-trial analysis, the advantage disappeared once both diets were cutting calories. When only weight-loss diets were compared, low-fat and high-fat versions did not differ for total or LDL cholesterol.

Saturated fat does more of the work

An older meta-analysis of 37 dietary intervention studies, not all of them randomized, looked at the official low-fat diets of the time. The stricter Step II diet lowered LDL by 16 percent, which was 25 mg/dL (0.65 mmol/L), and the Step I diet by 12 percent, or 19 mg/dL (0.49 mmol/L). For every 1 percent of energy taken off saturated fat, LDL fell by 1.9 mg/dL (0.05 mmol/L). In the Women's Health Initiative trial, a lipoprotein subsample of 2,730 postmenopausal women followed for about eight years, the LDL fall varied with how much saturated or trans fat the women reported cutting.

Hard outcomes come from saturated fat trials

No trial has measured heart attacks or deaths for cutting total fat on its own. The outcome trials cut saturated fat. A 2020 Cochrane review of 15 trials in about 59,000 people, lasting at least two years, found 21 percent fewer combined cardiovascular events (risk ratio 0.79, 95% CI 0.66 to 0.93, moderate certainty) with no clear change in deaths. The abstract gives this as a relative figure, and we did not have the absolute event rates. It reports the changes in LDL and total cholesterol only as small.

Unsettled. A 2026 review of 17 trials in 66,337 people read the same body of evidence by baseline risk. For people at low cardiovascular risk it found little or no benefit from cutting saturated fat over five years, and for people at high risk a likely important benefit, at low to moderate certainty. Where you start seems to decide whether the change matters.

Women before and after menopause

A meta-analysis of 8 trials in 1,536 women found a low-fat diet lowered LDL by 9.3 mg/dL (0.24 mmol/L), and HDL with it. Its conclusion names premenopausal women. In postmenopausal women the effect did not reach significance, a split based on a small number of studies.

Who should be careful

Not for everyone. Cutting fat usually means eating more carbohydrate, and that has a cost. In the 20-trial meta-analysis, low-fat diets lowered HDL cholesterol by 2.57 mg/dL and raised triglycerides by 11.68 mg/dL against high-fat diets. If your triglycerides or HDL are already a concern, that is the direction to watch.

Children are the group where a fat-restricted diet raises the most questions. A 2018 Cochrane review of children aged 2 to 18 found that a diet with 30 percent of energy or less from fat probably lowered LDL slightly, by 4.6 mg/dL (0.12 mmol/L) over six to 12 months. That estimate comes from one randomized trial of 618 children. Height after more than five years showed no clear difference, on low-quality evidence. In the Finnish STRIP trial, children counselled from infancy to eat less saturated fat had iron and zinc intake and blood markers no different from controls at age 3 to 4, in a subsample of 79. We found no trial data on low-fat diets for children under 2.

The opposite end matters too. A 2026 network meta-analysis of 47 trials in 3,450 adults aged 35 to 75 with at least one cardiovascular risk factor found ketogenic diets raised LDL by 17 mg/dL (95% CI 5 to 29; metric: 0.43 mmol/L, 0.13 to 0.74) against low-fat diets with moderate carbohydrate. If you have high cholesterol and are considering a very high-fat diet, that number is worth knowing.

What expert bodies say

The American Heart Association, in a 2017 presidential advisory, says that replacing saturated with unsaturated fats lowers LDL cholesterol, a cause of atherosclerosis. Its advice is to swap the type of fat within a DASH or Mediterranean pattern. That is a different instruction from simply eating less fat. We found the 2023 WHO guideline on saturated and trans fat and the US Dietary Guidelines for 2025 to 2030, but could not retrieve their wording directly, so we do not quote them here.

How we searched

What would change this answer

• A trial with heart attacks or deaths as its outcome that cuts total fat while holding saturated fat steady. Without one, the outcome evidence belongs to saturated fat.
• Trial data on fat restriction in children under 2, where we found none.
• Head-to-head comparison of what replaces the fat. The HDL and triglyceride cost depends on whether fat is swapped for refined starch, whole grains or unsaturated oils, and the trials we read did not separate these.
• We found no registered trial of low-fat diets and cholesterol under way.

Sources

1. ev-dfchol-01 · Meta-analysis or systematic review · systematic review and meta-analysis of randomized controlled trials · n = 57079
   The reduction in body weight was reflected in small reductions in LDL (-0.13 mmol/L, 95% CI -0.21 to -0.05), and total cholesterol (-0.23 mmol/L, 95% CI -0.32 to -0.14), with little or no effect on HDL cholesterol (-0.02 mmol/L, 95% CI -0.03 to 0.00), triglycerides (0.01 mmol/L, 95% CI -0.05 to 0.07)
   
   Who: adults not aiming to lose weight, randomized to lower versus higher fat intake for at least six months
   Effect: LDL -5 mg/dL (95% CI -8.1 to -1.9; metric: -0.13 mmol/L, -0.21 to -0.05); total cholesterol -8.9 mg/dL (95% CI -12 to -5.4; metric: -0.23 mmol/L, -0.32 to -0.14); HDL -0.77 mg/dL (95% CI -1.2 to 0; metric: -0.02 mmol/L, -0.03 to 0.00); triglycerides 0.89 mg/dL (95% CI -4.4 to 6.2; metric: 0.01 mmol/L, -0.05 to 0.07); GRADE high consistency
   Certainty: Direct answer to H1 from the strongest synthesis. The effect is small (~5 mg/dL LDL); part of it is through a weight loss of 3.1 lb (1.4 kg).
   Cochrane Database Syst Rev, 2020 · checked 2026-10-06 · we read the abstract
2. ev-dfchol-02 · Meta-analysis or systematic review · systematic review and meta-analysis of randomized controlled trials · n = 32 RCTs
   Decreases in total cholesterol (weighted mean difference -4.55 mg/dL [-0.12 mmol/L], 95% CI -8.03 to -1.07; P=0.01) and low-density lipoprotein (LDL) cholesterol (weighted mean difference -3.11 mg/dL [-0.08 mmol/L], 95% CI -4.51 to -1.71; P<0.0001) were significantly more pronounced following low-fat diets
   
   Who: overweight or obese adults, low-fat versus high-fat diets for at least 12 months
   Effect: LDL WMD -3.11 mg/dL (95% CI -4.51 to -1.71); total cholesterol WMD -4.55 mg/dL (95% CI -8.03 to -1.07); difference abolished in hypocaloric diets only
   Certainty: Long horizon; the effect on LDL is clinically small and disappears at an equal calorie deficit.
   J Acad Nutr Diet, 2013 · checked 2026-10-06 · we read the abstract
3. ev-dfchol-03 · Meta-analysis or systematic review · systematic review and meta-analysis of randomized controlled trials · n = 32 RCTs
   Including only hypocaloric diets, the effects of low-fat vs high-fat diets on total cholesterol and LDL cholesterol levels were abolished.
   
   Who: overweight or obese adults on hypocaloric low-fat versus high-fat diets for at least 12 months
   Effect: hypocaloric subgroup: no difference in total or LDL cholesterol between low-fat and high-fat diets
   Certainty: Suggests that on weight-loss diets the fat share barely matters for LDL; the fat type matters.
   J Acad Nutr Diet, 2013 · checked 2026-10-06 · we read the abstract
4. ev-dfchol-04 · Meta-analysis or systematic review · systematic review and meta-analysis of randomized controlled trials · n = 2106
   Conversely, significant higher level of TAG (WMD: 11·68 mg/dl (0·13 mmol/l), 95 % CI 5·90, 17·45; P<0·001) and lower level of HDL-cholesterol (WMD: -2·57 mg/dl (-0·07 mmol/l); 95 % CI -3·85, -1·28; P<0·001) were found following low-fat diets compared with high-fat diets.
   
   Who: people with overweight or obesity without overt metabolic disturbance
   Effect: LDL WMD -4.41 mg/dL (95% CI -7.81 to -1.00); HDL WMD -2.57 mg/dL (95% CI -3.85 to -1.28); triglycerides WMD +11.68 mg/dL (95% CI 5.90 to 17.45)
   Certainty: Trade-off: lower LDL at the cost of lower HDL and higher triglycerides (fat is replaced with carbohydrates).
   Br J Nutr, 2018 · checked 2026-10-06 · we read the abstract
5. ev-dfchol-05 · Meta-analysis or systematic review · systematic review and meta-analysis of randomized controlled trials · n = 2106
   Total cholesterol and LDL-cholesterol levels were lower following low-fat diets compared with high-fat diets: weighted mean difference (WMD) was -7·05 mg/dl (-0·18 mmol/l; 95 % CI -11·30, -2·80; P=0·001) and -4·41 mg/dl (-0·11 mmol/l; 95 % CI -7·81, -1·00; P=0·011), respectively.
   
   Who: people with overweight or obesity without overt metabolic disturbance
   Effect: total cholesterol WMD -7.05 mg/dL (95% CI -11.30 to -2.80); LDL WMD -4.41 mg/dL (95% CI -7.81 to -1.00)
   Certainty: Consistent with Cochrane 32476140 in size.
   Br J Nutr, 2018 · checked 2026-10-06 · we read the abstract
6. ev-dfchol-06 · Meta-analysis or systematic review · systematic review and meta-analysis of randomized controlled trials · n = ~59000
   There was little or no effect on cancer mortality, cancer diagnoses, diabetes diagnosis, HDL cholesterol, serum triglycerides or blood pressure, and small reductions in weight, serum total cholesterol, LDL cholesterol and BMI.
   
   Who: adults with or without cardiovascular disease, randomized to reduced saturated fat for at least 24 months
   Effect: combined CVD events RR 0.79 (95% CI 0.66 to 0.93), 11 trials, 53,300 participants, GRADE moderate; all-cause mortality RR 0.96 (95% CI 0.90 to 1.03); small reductions in total and LDL cholesterol
   Certainty: LDL/TC numbers could not be obtained from the full text (PMC7388853 no_fulltext); the abstract says only 'small reductions'.
   Cochrane Database Syst Rev, 2020 · checked 2026-10-06 · we read the abstract
7. ev-dfchol-07 · Observational data · meta-analysis of dietary intervention studies in free-living subjects, randomization not required · n = 37 studies
   Multiple regression analyses showed that for every 1% decrease in energy consumed as dietary saturated fatty acid, TC decreased by 0.056 mmol/L and LDL cholesterol by 0.05 mmol/L.
   
   Who: free-living subjects in 37 dietary intervention studies published 1981 to 1997
   Effect: LDL -19 mg/dL (-0.49 mmol/L) (12%) Step I and -25 mg/dL (-0.65 mmol/L) (16%) Step II; per 1% energy less saturated fat LDL -1.9 mg/dL (-0.05 mmol/L); HDL -7% on Step II
   Certainty: Old synthesis, not only RCTs; reference figures for NCEP diets, where saturated fat itself sets the effect.
   Am J Clin Nutr, 1999 · checked 2026-10-06 · we read the abstract
8. ev-dfchol-08 · Randomized controlled trial(s) · randomized controlled trial, lipid substudy · n = 2730
   Reductions in LDL cholesterol varied by quartile of reported lowering of saturated or trans fat.
   
   Who: postmenopausal women; lipoprotein subsample of 2730 participants, mean follow-up 8.1 years
   Effect: fat intake 7.8% of energy lower at year 6; HDL change -1.6, -0.7 and -1.0 mg/dL at 1, 3 and 6 years; LDL fall varied by quartile of saturated or trans fat lowering
   Certainty: The largest RCT of a low-fat pattern; the HDL decrease is clinically insignificant.
   Am J Clin Nutr, 2010 · checked 2026-10-06 · we read the abstract
9. ev-dfchol-09 · Meta-analysis or systematic review · risk-stratified systematic review of randomized trials with GRADE · n = 66337
   For persons at low cardiovascular risk, reducing or modifying saturated fat intake has little or no benefit over a period of 5 years.
   
   Who: adults with or without cardiovascular disease in 17 randomized trials of reducing or modifying saturated fat
   Effect: all-cause mortality RR 0.96 (95% CI 0.88 to 1.06); nonfatal MI RR 0.86 (95% CI 0.70 to 1.06); with polyunsaturated replacement nonfatal MI RR 0.75 (95% CI 0.58 to 0.99); low to moderate certainty
   Certainty: The newest synthesis (to July 2025); diverges from Cochrane 2020 in interpretation: benefit depends on baseline risk.
   Ann Intern Med, 2026 · checked 2026-10-06 · we read the abstract
10. ev-dfchol-10 · Meta-analysis or systematic review · network meta-analysis of randomized clinical trials · n = 3450
    Ketogenic diets showed the largest increases in LDL cholesterol [0.43 mmol/L (0.13; 0.74)] total cholesterol [0.55 mmol/L (0.13; 0.96)] and HDL cholesterol [0.12 mmol/L (0.06; 0.18)], compared with the reference diet
    
    Who: adults aged 35 to 75 with at least one cardiovascular risk factor
    Effect: ketogenic vs low-fat-moderate-carbohydrate: LDL +17 mg/dL (95% CI 5 to 29; metric: 0.43 mmol/L, 0.13 to 0.74), total cholesterol +21 mg/dL (95% CI 5 to 37; metric: 0.55 mmol/L, 0.13 to 0.96), HDL +4.6 mg/dL (95% CI 2.3 to 7; metric: 0.12 mmol/L, 0.06 to 0.18)
    Certainty: Axis 6 for the opposite side of the question: a very high-fat diet raises LDL.
    Eur J Nutr, 2026 · checked 2026-10-06 · we read the abstract
11. ev-dfchol-11 · Meta-analysis or systematic review · systematic review and meta-analysis of randomized controlled trials · n = 1536
    A low-fat diet is efficacious in reducing TC, HDL-C, and LDL-C in premenopausal women.
    
    Who: premenopausal and postmenopausal women, low-fat versus usual diet
    Effect: TC -0.49 mmol/L (95% CI -0.69 to -0.29); LDL -9.3 mg/dL (95% CI -15 to -3.5; metric: -0.24 mmol/L, -0.38 to -0.09); HDL -4.6 mg/dL (95% CI -7.7 to -1.9; metric: -0.12 mmol/L, -0.20 to -0.05); postmenopausal subgroup not significant
    Certainty: HDL also falls; the menopause subgroup is a small number of studies.
    Menopause, 2014 · checked 2026-10-06 · we read the abstract
12. ev-dfchol-12 · Randomized controlled trial(s) · Cochrane systematic review of randomized trials and cohort studies; lipid estimates from one RCT · n = 618
    Lower fat intake probably slightly decreased low-density lipoprotein (LDL) cholesterol over six to 12 months (MD -0.12 mmol/L, 95% CI -0.20 to -0.04; 1 RCT; n = 618, moderate-quality evidence)
    
    Who: children aged 24 months to 18 years, lower fat (30% of energy or less) versus usual fat intake
    Effect: LDL -4.6 mg/dL (95% CI -7.7 to -1.5; metric: -0.12 mmol/L, -0.20 to -0.04) at 6-12 months, 1 RCT, moderate quality; height after more than five years MD -0.24 in (95% CI -0.81 to 0.34; metric: -0.60 cm, -2.06 to 0.86), low quality
    Certainty: Estimates from one RCT (DISC/STRIP); growth safety: low-quality evidence. No data for children under 2 years.
    Cochrane Database Syst Rev, 2018 · checked 2026-10-06 · we read the abstract
13. ev-dfchol-13 · Randomized controlled trial(s) · randomized controlled trial (STRIP), nutrient status substudy · n = 79
    In conclusion, long-term supervised use of a diet low in saturated fat and cholesterol did not influence intake or serum indicators of iron and zinc in children.
    
    Who: children aged 3 to 4 years in the STRIP trial, 40 intervention and 39 control
    Effect: iron intake 8.8 vs 8.6 mg/day; ferritin 21.8 vs 19.2 ug/L; zinc 7.5 vs 7.4 mg/day; no significant differences
    Certainty: Small subsample; removes part of the fear of iron deficiency on a supervised low-fat diet.
    Am J Clin Nutr, 1997 · checked 2026-10-06 · we read the abstract
14. ev-dfchol-14 · Position of an expert body · presidential advisory, narrative review of trials and cohorts · n = —
    Replacement of saturated with unsaturated fats lowers low-density lipoprotein cholesterol, a cause of atherosclerosis, linking biological evidence with incidence of CVD in populations and in clinical trials.
    
    Who: general population, United States
    Effect: position: replace saturated fat with unsaturated fat within a DASH or Mediterranean pattern
    Certainty: Authority position; the ≈30% CVD reduction in RCTs is an AHA estimate, not a meta-analysis in this card.
    Circulation, 2017 · checked 2026-10-06 · we read the abstract