It sounds simple enough: Eat within a narrow window, fast for the rest, lose weight.
Except there are always those for whom it doesn’t work.
While some people may simply not be well suited to intermittent fasting, many who fail to lose—or even gain weight—may be sabotaged by biological processes at work in their bodies.
Intermittent fasting isn’t failing because the science is wrong. It’s failing because most people don’t understand the biological rules that make it work.
Breaking the Fast Too Early
It takes 16 to 24 hours for the body to deplete its stored glucose and switch to burning ketone for fuel. Most people end up interrupting this switch by eating small amounts of carbohydrates. A high-carbohydrate meal, meanwhile, can delay the switch to ketones from happening for days.
Overeating and Eating Too Late
Many intermittent fasters go into this dietary approach without guidance from dietitians. As a result, they end up overeating in their meal window or eating too late in the day, which can undermine their fast.
High Stress and Hormones
Your body’s stress load can blunt the benefits of fasting, even if you’re following the schedule perfectly.
Chronic stress and poor sleep keep cortisol elevated, which increases hunger and cravings for high-fat, high-sugar foods and promotes fat storage—even if you’re eating less as a result of your fasting.
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