Does Coconut Oil Shrink Your Waist? What the Studies Show

Does Coconut Oil Shrink Your Waist? MCTs and the Evidence

Can a daily spoonful of coconut oil trim your waistline? The honest answer is: probably not in any way that matters. A handful of small studies reported slightly smaller waists in people taking coconut oil, but the best-controlled trials and a large 2020 review found no meaningful effect on weight or body fat, along with a clear rise in LDL cholesterol. Here is where the idea came from, what the studies actually measured and how to think about coconut oil in your kitchen.

Where the claim comes from: medium-chain fats

Most fats in our diet are long-chain triglycerides, with fatty acids of 14 or more carbon atoms. Medium-chain triglycerides (MCTs) have shorter tails, usually defined as 6 to 12 carbons. Caprylic acid (8 carbons) and capric acid (10 carbons) are the classic examples.

That shorter length changes how the body handles them. MCTs do not need bile to be absorbed. They pass from the gut straight into the portal vein and travel to the liver, where they are broken down quickly for energy or turned into ketones. Long-chain fats, by contrast, are packaged into particles that circulate through the lymph and bloodstream and are more easily stored in fat tissue.

Because of this, purified MCT oil has been used for decades in clinical nutrition, for example in people who cannot absorb normal fat and in some ketogenic diets for epilepsy. Researchers also noticed that MCTs seemed to raise energy expenditure a little and to make people eat slightly less at their next meal. Those findings are the root of the coconut oil weight-loss story.

Why coconut oil is not the same as MCT oil

Coconut oil is often described as nature's richest source of MCTs, and that is where the logic starts to slip. About 82 percent of its fat is saturated. Per 100 grams, USDA figures list roughly:

Lauric acid (12 carbons): 41.8 g
Myristic acid (14 carbons): 16.7 g
Palmitic acid (16 carbons): 8.6 g
Caprylic acid (8 carbons): 6.8 g
Smaller amounts of capric acid and unsaturated fats

The fast-burning MCTs studied in weight research, caprylic and capric acids, make up only a modest share. The biggest component, lauric acid, sits at the edge of the medium-chain definition, and many nutrition researchers argue that a large share of it behaves more like a long-chain fat in the body. In fact, lauric acid is commonly removed when manufacturers make MCT oil. So results from MCT oil studies cannot simply be transferred to a jar of coconut oil.

Palm kernel oil has a very similar profile, and human breast milk contains lauric acid too. Comparisons with breast milk are often used to make coconut oil sound uniquely wholesome, but sharing one fatty acid does not make two foods nutritionally alike.

The studies behind the waist headline

The headline that coconut oil shrinks your waist traces back to a few small trials:

A one-month pilot in Malaysia

In an open-label pilot study published in 2011, Liau and colleagues gave 20 overweight adults about two tablespoons of virgin coconut oil a day for four weeks. The men's waists shrank by roughly an inch on average. However, there was no control group, so the change could reflect people eating more carefully simply because they were in a diet study.

Small controlled trials

A controlled trial published in 2015, with around 100 participants taking about a tablespoon a day for three months, reported a waist reduction of nearly an inch compared with controls, but the controls received nothing at all rather than a placebo oil. In a 2019 Brazilian study of just 20 women who also walked three times a week, the coconut oil group's waist measurement fell by about 2.6 percent, yet their weight, body fat percentage and lean mass did not change, which the authors themselves noted.

Trials with a proper comparison

When coconut oil has been tested against another oil, or against a placebo, the picture fades. In one trial comparing two tablespoons of coconut oil with soybean oil daily, waist changes did not differ between groups. A placebo-controlled study published in 2017 found no significant changes in weight, waist, hip measurements, total fat or belly fat.

A small 1980s study is also often cited for showing that a 400-calorie MCT meal raised metabolic rate more than a long-chain fat meal over six hours. Even if accurate, a temporary bump in calorie burning after one meal is a long way from proven fat loss, and that study used MCTs, not coconut oil.

What larger reviews conclude

Single small studies point in different directions, so reviews that pool many trials are more reliable. The most important one here is a 2020 systematic review and meta-analysis by Neelakantan and colleagues in the journal Circulation, which combined 16 trials comparing coconut oil with other fats for at least two weeks.

Body weight and body fat: no significant effect compared with non-tropical vegetable oils.
LDL cholesterol: higher by about 10.5 mg/dL on average with coconut oil.
HDL cholesterol: higher by about 4 mg/dL.
Blood sugar and inflammation markers: no significant effect.

The authors concluded that coconut oil should not be viewed as a healthy oil for reducing cardiovascular risk. A 2017 presidential advisory from the American Heart Association had already advised against using it, because it raises LDL, a well-established cause of heart disease. Many other health bodies, including the WHO and the UK's NHS, recommend limiting saturated fats such as coconut oil.

Pure MCT oil is a separate question. A 2020 meta-analysis found that MCTs reduce how much people eat afterwards compared with long-chain fats, and some trials suggest a small benefit for weight loss, but results are inconsistent and the effects are modest.

Myths worth retiring

"MCTs are burned, never stored." They are used for energy more readily, but any surplus calories, from any source, can still end up as body fat.
"Eat coconut oil and lose weight without cutting calories." Coconut oil supplies about 120 calories per tablespoon. Adding two tablespoons a day to an unchanged diet adds around 240 calories.
"Ancient traditions prove it works." Coconut has a long place in many cuisines and in Ayurvedic practice, but tradition is not evidence of fat loss. Bold statements about lauric oils, such as those often attributed to the lipid researcher Jon Kabara, are opinions rather than trial results.
"Saturated fat from plants is different." For LDL cholesterol, coconut oil behaves much like other saturated fats, and in trials it raised LDL more than unsaturated oils.

Practical takeaways

Coconut oil is a perfectly good ingredient in moderation. It adds a distinctive flavour to curries, baking and stir-fries, and an occasional spoonful will not harm a healthy person. It is just not a slimming tool.

Use it for taste, not as a supplement. If you want to cook with it, swap it for another fat rather than adding it on top.
For everyday cooking, oils rich in unsaturated fats, such as olive, rapeseed (canola) or sunflower oil, have the stronger evidence for heart health.
For a smaller waist, the steady basics still work best: an overall calorie balance, plenty of vegetables, fibre and protein, regular movement and good sleep.
If you have high cholesterol, heart disease or diabetes, or you are thinking about MCT oil, talk to a doctor before making big changes.

The coconut oil story is a good example of how a real biological detail, the way medium-chain fats are absorbed, can be stretched into a promise the evidence does not support.

Sources: American College of Cardiology: summary of the 2020 coconut oil meta-analysis; Wikipedia: Coconut oil; Wikipedia: Medium-chain triglyceride; NutritionFacts.org: Coconut oil and abdominal fat (review of trials); Otto and da Rocha, Journal of Physical Education (2019); earlier article via Organic Health.

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