Not all body fat is created equal. Fat that accumulates beneath the skin, subcutaneous fat, is much less harmful to health — conceivably not harmful at all — than fat around the midsection — belly fat, abdominal fat, or the term of art among scientists, visceral fat. And this belly fat promotes aging.
Visceral fat refers to body fat that is stored inside the abdominal cavity, around the internal organs (viscera), and it has uniquely harmful effects on health. For example, in older women, the ratio of waist to hip circumference is “strongly and positively associated with mortality in a dose-response manner“, and is a better marker of mortality and health risks than body mass index.
Visceral fat is a significant risk factor for breast cancer in women, and for prostate cancer in men. Visceral fat is a strong predictor of heart disease in men. The likely source for all of these risks is that visceral fat promotes insulin resistance and ultimately diabetes.
The health risks of visceral fat are well-known.
Insulin resistance, diabetes, and abdominal obesity together make up probably the most pro-aging formula around, as I discussed in my book Stop the Clock.
A common feature of life-extension interventions is that they decrease visceral fat. Calorie restriction, for example, the most potent life-extension procedure known, results in much lower levels of visceral fat. How important is this reduction to the effects of calorie restriction? Does reduction of visceral fat alone extend lifespan?
When animals have visceral fat surgically removed, they live longer. While they didn’t live as long as calorie-restricted animals, they lived longer than ad lib fed animals, showing that reduction of visceral fat could be an important component of calorie restriction and its anti-aging effects.
Indeed, some scientists believe that reduction of visceral fat is the main reason that calorie restriction extends lifespan.
Removal or reduction of visceral fat improves insulin sensitivity.
Until relatively recently, fat was thought to be just an inert storage material. It’s now known that fat produces hormones and cytokines, and that these play an important role in health. Increased visceral fat disrupts metabolism and increases health risks through these hormones and cytokines.
Methionine restriction also greatly extends lifespan. This intervention restricts the amount of only one amino acid, methionine, and this alone is enough to improve health and extend life.
Why methionine restriction does this has been the subject of a great deal of research and speculation. But a striking feature of methionine-restricted animals is that they have much less visceral fat. This is not due to eating less food, but to methionine restriction alone. The reduction in fat leads to insulin sensitivity on a par with young animals.
Bariatric surgery is performed on obese patients for weight loss. There are various forms this surgery takes, but they have in common a decrease in the amount of food energy either ingested or absorbed.
All forms of bariatric surgery that cause weight loss improve insulin sensitivity and in many cases cure diabetes. Does loss of fat or eating less cause the health benefits?
Curiously, insulin sensitivity increases within days of bariatric surgery, before any appreciable weight loss has occurred. What in the world is going on? Insulin sensitivity improves while these patients are still morbidly obese and without having lost much weight.
Two things, both related, are probably going on here.
One is that bariatric surgery, especially in the few days immediately post-surgery, amounts to a medically enforced fast. With patients unable to consume much energy, insulin drops, as it does with intermittent fasting.
Another is that the direction of energy flow, whether into or out of fat mass, matters. If someone takes in little food, then lipolysis occurs, and fat starts leaving adipose tissue to provide energy.
Both visceral fat mass and calorie intake matter.
Given the enormous health consequences of visceral fat, keeping it minimal is crucial. Here’s how you do that.
Sugar appears to be just about the worst thing you can ingest this side of poisonous mushrooms or liters of whisky. It’s implicated in obesity, diabetes, and heart disease. It’s likely a risk factor for colon cancer and pancreatic cancer, to name two.
Importantly for our purposes, sugar is associated with increased visceral fat. The following graph shows what happened to people who drank a liter of soda a day for 6 months, vs a liter of milk, diet soda, or water. Liver fat went up 130%. That’s very bad for your health.
Low-carbohydrate diets are better for weight loss than “healthy eating”.
Cutting carbs means avoidance of anything made with grains: breakfast cereal, bread, pasta, rice, etc. It also means avoiding starch, such as potatoes.
Intermittent fasting may be just as effective as calorie restriction at fighting aging. Fasting for 16 hours or more lowers insulin, which leads to increased lipolysis, or breakdown of body fat.
High-intensity exercise, but not low-intensity, decreases visceral fat. Twice-weekly resistance training decreases abdominal fat and improves insulin sensitivity.
Visceral fat is responsible for most if not all of the deleterious health effects of obesity. It shortens lifespan and is potently pro-aging, leading to increased risks of heart disease, cancer, and diabetes.
To avoid it or get rid of it, you should do the opposite of what most people are doing.