Back in the old hunter-gatherer days, the human species got a lot of use out of the hormone cortisol. That's the stress hormone activated during the fight-or-flight response, causing our blood pressure to rise and heart rate to increase.
Throw in a little adrenaline and these useful, even essential, physical adjustments made it possible for our forebears to do things like battle marauding tigers on a moment's notice, or scoop up their offspring and flee from raging wildfire.
But in the modern world, there's little need to either fight or flee, yet the cortisol release remains functional in the species, only now, it's activated in response to the stressors of modern society-bad traffic, malfunctioning machinery, domestic discord-rather than natural perils or challenges to survival.
There are some real downsides to this artifact of our rugged past. Research indicates that cortisol is also associated with abdominal fat production. And without the physical release demanded by, say, wrangling an enraged wildebeest, cortisol seems to end up accelerating abdominal fat production.
For virtually anyone, this can lead to higher cholesterol levels, blood sugar levels and elevated blood pressure, all factors for heart disease. But people who are genetically prone to holding their fat stores around the middle are especially susceptible, which makes this a bigger concern for these apple-shaped people than it is for those pear-shaped individuals who tend to carry their extra on the hips and thighs.
And there is other research that shows that abdominal fat retention--distinct from lower-body fat retention--causes specific, recognizable chemical changes in the body that can ultimately lead to lowered metabolism and symptomatic cravings for sweets.
In this way, abdominal fat retention can lead to ever more weight gain, putting overweight people with a predisposition to the apple shape at a much elevated risk for disease. Add a stressful lifestyle and excess cortisol production to those factors, and you have a time-tested recipe for a heart attack.