Food Literacy
The first time we wrote about fat, we meant the fat on your plate: what it builds, why your brain is roughly 60% fat by dry weight, and how three decades of low-fat messaging got the story wrong. That article was about the fat you eat.
This one is about the fat you carry. The part that surprises most people is that the amount matters less than the address.
Two people can weigh the same and wear the same size while storing that weight in completely different places. One stores it under the skin, where you can pinch it. The other stores it deep in the abdomen, packed around the liver and intestines, where there is nothing to pinch. The second person often looks like the healthier of the two.
The principle. Body fat is not inert storage. It is an active endocrine organ that releases hormones and inflammatory signals into your bloodstream, and the portion packed around your organs behaves very differently from the portion sitting under your skin.
Two Kinds of Fat, One Word
We use one word, “fat,” for two tissues that do different jobs.
| Subcutaneous fat | Visceral fat | |
|---|---|---|
| Where it sits | Under the skin | Behind the abdominal wall, around the organs |
| Can you pinch it | Yes | No |
| Shows on the scale | Yes | Yes, but indistinguishably |
| Metabolically active | Somewhat | Considerably more |
| Drains into | General circulation | The portal vein, straight to the liver |
That last row does most of the work. Visceral fat empties into the portal vein, delivering its output straight to your liver before the rest of the body sees any of it. Subcutaneous fat has no such shortcut.
So a person can carry a risky amount of visceral fat at a weight nobody would comment on. Thomas and colleagues (Obesity, 2012) used MRI to map where fat actually sits and named the pattern TOFI, thin on the outside, fat on the inside: a normal BMI hiding a large internal fat depot. The mirror and the pinch test measure the fat that matters least.
What Visceral Fat Does While You Are Not Thinking About It
It files away your vitamin D. Vitamin D is fat soluble, so it dissolves into fat tissue instead of circulating where your body can use it. Wortsman and colleagues (American Journal of Clinical Nutrition, 2000) gave participants whole-body UV light and found people with obesity reached peak blood levels roughly 57% lower than those without, from the same dose. Same sunlight, less delivered. If you get sun, supplement, and still cannot move your numbers, body composition is worth looking at.
It makes its own estrogen. Fat tissue expresses aromatase, the enzyme that converts androgens such as testosterone into estrogens, so more fat tissue generally means more of that conversion. Wang and colleagues (Journal of Steroid Biochemistry and Molecular Biology, 2015) describe aromatase overexpression in dysfunctional fat tissue as one link between obesity and postmenopausal breast cancer risk. In men, the same conversion is associated with lower testosterone. Worth knowing: one drug class used against certain breast cancers is an aromatase inhibitor, aimed at that enzyme.
It interrupts the message that you are full. Leptin is how fat tissue tells your brain there is enough stored energy on board. More fat means more leptin, and over time the brain appears to stop responding properly, a pattern called leptin resistance (Myers and colleagues, Trends in Endocrinology and Metabolism, 2010). Whether that causes weight gain or follows from it is debated. Either way, more fat does not produce a stronger stop signal.
Your Fat Cells Run Short of Oxygen. Then Your Immune System Shows Up.
Fat cells can expand faster than the blood vessels feeding them. Trayhurn (Physiological Reviews, 2013) laid out the consequence: enlarged fat tissue becomes relatively hypoxic. Stressed and dying fat cells attract immune cells, which release inflammatory molecules including TNF-alpha, first tied to fat tissue and insulin resistance by Hotamisligil and colleagues (Science, 1993). Your liver answers those signals by producing C-reactive protein.
That matters practically, because CRP appears on ordinary blood panels. A raised hs-CRP tells you inflammation is happening somewhere, not where. Visceral fat is a common answer and one of the few you can directly change. It shows up in outcomes too: Pischon and colleagues (New England Journal of Medicine, 2008) followed roughly 360,000 people across Europe and found waist circumference associated with mortality risk independent of BMI. Same BMI, different waists, different risk.
The Part Almost Nobody Mentions
Fat is also where your body files fat-soluble compounds it cannot immediately clear. Many industrial pollutants are lipophilic: they dissolve into fat rather than water. Persistent organic pollutants such as PCBs and dioxins accumulate there over years. In the short term that is arguably protective, since a compound parked in fat is not circulating past every cell you own.
The complication arrives when the fat comes off. Chevrier and colleagues (International Journal of Obesity, 2000) measured pollutant concentrations in people losing weight and found plasma levels rose as fat mass fell. Cheikh Rouhou and colleagues (Diabetes and Metabolism, 2016) later asked whether that release explains some of the adverse effects seen after weight loss. The question is open. The release is well documented.
Two compounds in this category already have entries on our list: BPA, the can-lining chemical, and PFAS, the forever chemicals.
Where Diet Discipline Stands
This is where somebody usually tries to sell you a detox protocol, so we will separate the evidence from our opinion.
The evidence: fat tissue stores these compounds, and losing fat releases them into circulation. Measured in humans, repeatedly. Not established: that any cleanse, supplement stack or detox program improves how your body handles that release. We have not found good human evidence for it, and we will not imply otherwise because the mechanism sounds convincing.
Our position: the answer to a real mechanism is not a product, it is a pace and a direction. Take fat off steadily rather than as fast as possible, reduce what is arriving now, and support the routes your body already uses, which run on fiber, water and regular bowel movements rather than on anything you have to buy.
Myth vs Reality
Myth: If I cannot pinch it, I do not have it.
Reality: Visceral fat sits behind the abdominal wall, out of reach of the pinch test.
Myth: A normal BMI means normal metabolic health.
Reality: BMI describes weight against height and says nothing about where that weight sits, which is why TOFI exists as a described pattern.
The Protocol
1. Measure your waist. It takes 60 seconds. Tape measure level with the navel, exhale normally, do not suck in. Divide by your height in the same units. A waist-to-height ratio under 0.5 is the common rule of thumb, and it needs no appointment.
2. Ask for the markers that see inside. At your next blood draw: fasting glucose or HbA1c, triglycerides and HDL, hs-CRP, vitamin D. Those four say more about visceral fat than the scale does.
3. Choose steady over rapid. Slower fat loss is not weaker discipline. Given what the fat is holding, it is the more considered choice.
4. Reduce what comes in. Cook and store in glass or stainless rather than plastic, skip food that arrives in grease-resistant wrappers, and read the packaging as carefully as the label.
5. Support what goes out. Most people run a 10 to 20 gram daily fiber gap, and hydration is the other half.
What to Watch Over 4 to 12 Weeks
Waist measurement, taken the same way on the same day of the week. It often moves before the scale does, and it tracks the fat you actually care about. On repeat bloodwork, hs-CRP and triglycerides tend to respond sooner than people expect. Also notice whether meals hold you longer than they used to. Subjective, but it is the change people report first.
For context: 72.4% of American adults aged 20 and over are overweight or have obesity, per CDC National Center for Health Statistics data for August 2021 to August 2023. If that describes you, you are the majority, not an outlier.
Your action step, today. Find a tape measure. Measure your waist at the navel, divide by your height, and write both numbers down with today’s date.
That one ratio tells you more about the fat that matters than your scale has told you all year, and you can repeat it at home, for free, for the rest of your life.
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