Chapter 71
Not All Fat Calories Are the Same
As we age, fat tends to migrate from the flabby fat under the skin (subcutaneous fat) into deeper depots, wrapping around internal organs and making a thick belly (visceral fat), especially in women. Between the ages of 25 and 65, women lose nearly six kilos of bone and muscle mass, while the proportion of their belly-fat stores quadruples. (In men, these belly-fat stores usually only double.) So it may be that the bathroom scale no longer shows it, yet a woman has still accumulated more of the most dangerous fat. Even at the same total fat mass or the same BMI: The larger the waist circumference, the lower the life expectancy.
Visceral fat is the fat that kills us. In contrast, subcutaneous fat is relatively harmless. The New England Journal of Medicine published a study of 15 women with obesity who were examined before and after nearly 20 pounds of surface fat were suctioned out, which for them meant getting rid of about 20 percent of their total body fat. Normally, blood sugar, inflammation, blood pressure, cholesterol, and triglycerides go down when you lose 5 to 10 percent of your body weight as fat, but after this massive liposuction, none of these positive effects appeared. That suggests that the fat under the skin is not the problem; rather, the deep belly fat causes the metabolic damage in obesity. The good news is that the most dangerous fat is also the easiest to lose. Our body most prefers to give up the evil visceral fat first. And with lifestyle interventions, older people lose just as much weight as younger people.
That visceral fat shortens life has been demonstrated in rats. Surgical removal significantly extended both average and maximum life span. And in humans? Those who lose weight through bariatric surgery live significantly longer than similarly heavy affected individuals in control groups who are not operated on (details in the video see.nf/bariatric), but there are still no randomized studies to confirm this. However, there are randomized studies on losing weight through diet and lifestyle interventions.
Not All Fat Calories Are the Same
A meta-analysis of 15 studies in which men and women were randomized to a weight-loss program for up to twelve years found that weight loss not only reduces inflammation, blood pressure, blood sugar, and disabilities, but lengthens life and lowers the risk of early death by about 15 percent. So which diet makes the most sense for losing weight?
The best results came from a whole-food, plant-based diet: With it, the greatest weight loss yet published in the medical literature was achieved at six and at twelve months compared to all other dietary patterns in randomized controlled trials that likewise neither restricted calories nor prescribed exercise. One of the causes could be the reduced fat intake. Randomized participants eating a low-fat plant-based diet naturally ate 600 fewer calories a day than participants who were prescribed a high-fat ketogenic diet. That led to a significant loss of body fat and preservation of lean body mass—the opposite of what was observed in participants in the ketogenic group, who could not record any significant losses in body fat, but whose lean body mass decreased, because their bodies attacked their own protein (even though the participants consumed more protein).
So fat is not the same as fat.
In How Not to Diet, I debunk the myth that “a calorie is a calorie.” Whether you gain weight from consuming that calorie or not depends on its source. For example, if you eat approximately the same number of calories and the same amount of fat, but replace the fats from meat and butter with nuts, avocados, and olive oil, you can lose up to six pounds more within a month. Saturated fat can also cause twice as much belly fat as consuming other fats in the same amount. Why? One of the reasons saturated fats make you fatter is that they are more likely to be stored immediately rather than burned. For example, oleic acid, the most important monounsaturated fat in nuts, avocados, and olives, is burned 20 percent faster than palmitic acid, which is found mainly in meat and dairy products and is the predominant saturated fat in the American diet. In fact, in a petri dish you can drip palmitic acid onto muscle cells and illustrate how fat utilization is suppressed.
If you want to learn more about why healthy eating makes weight loss so efficient, get How Not to Diet from the library.
Brown Fat Tissue
When we come into the world, wet and smeared, we go straight from the cozy 37 degrees of the womb out into room temperature. To maintain our temperature, we warm-blooded mammals developed a unique organ 150 million years ago: brown fat tissue. In response to external cold, it generates heat from fat. White fat in the belly stores fat, but brown fat in the neck and shoulder region burns fat. Activating brown fat can not only mitigate the age-related decline in basal metabolic rate; it may also play a role in how long we live.
Longer-lived animals have more active brown fat, short-lived ones less active, and in mice a longevity gene was found that boosts the activity of brown fat tissue. When brown fat tissue was removed from mice or transplanted among the animals, its influence on a healthy aging process was confirmed. If that also applies to humans, it could help explain, among other things, why women live longer than men, because women have more brown fat tissue throughout their lives. Activating brown fat promotes the secretion of the fasting and longevity hormone FGF21 (see the chapter Protein Restriction), but unfortunately it declines with age. In people under 40, cold stimulates brown fat by up to 100 percent, but in older people this activity can fall to under 10 percent.
But you do not have to stay outside in the cold now. As I describe in How Not to Diet, there are foods that can rev up the performance of brown body fat. Components in chili pepper do this, for example, and they were tested in participants up to 64 years old. The dose is about one raw chili pepper or half a teaspoon of red paprika powder a day. So it does not get too spicy, chop the pepper very finely or add it to a soup or to the whole-food “V8” vegetable smoothie from one of my cooking videos at NutritionFacts.org. Alternatively, you can also use ginger powder. It promotes weight loss (brown fat tissue is presumably behind it) at one teaspoon per day, and you can simply stir that into hot water and make ginger tea.
How Much Should You Weigh to Live a Long Time?
We seem to have gotten used to the deadly threat posed by obesity. In the professional literature from about 50 years ago, when obesity was not yet commonplace, it was portrayed far more grimly: “Obesity is always tragic, and the danger it poses is dreadful.” But it is not only obesity. Of the four million deaths per year attributed to an excess of body fat, almost 40 percent of the victims are only overweight, not obese.
But what about the so-called obesity paradox, study results suggesting that people who are overweight live longer? The Global Mortality BMI Collaboration cleared up this myth, based on data from hundreds of studies with more than ten million people in dozens of countries around the world (details at see.nf/paradox). So what is the optimal BMI?
The most comprehensive studies in the United States and worldwide found that a normal body mass index between 20 and 25 is associated with the highest life expectancy. If you look at the best available studies with the longest follow-ups, this range can be narrowed further, namely to 20–22, meaning about 57.5 to 63.5 kilos for a person about 1.70 meters tall. You can use the table to see where your ideal weight lies for your height.