Intermittent fasting is growing in popularity, but is it good for your heart? Can it lower your cholesterol? Our Registered Dietitian answers all of your intermittent fasting questions below!
Intermittent fasting is simply when you alternate periods of fasting - or not eating - with periods of eating. Traditionally, people have fasted for religious reasons, but intermittent fasting is gaining popularity due to claims that it leads to weight loss, lower cholesterol and blood pressure, and longer lifespan.
Methods of intermittent fasting
The most popular methods of intermittent fasting are the 5:2 and the 16:8. The 5:2 (alternate day fasting) is when you eat 500 calories two days per week and a normal amount of calories the other days of the week, while still aiming to eat healthy foods every day. The 16:8 (time-restricted eating) is when you eat in an 8-hour window, typically 12 pm - 8 pm and fast for 16 hours. But you could get benefits by even doing a 12 hour fast overnight.
When we eat, the body breaks down food into glucose (sugar) for energy. Blood glucose then rises and insulin, a hormone, is released from the pancreas to take glucose from the blood to cells for energy. If there is glucose leftover, insulin will store it as glycogen in the muscle and liver and the rest will be stored as fat. In fact, insulin is sometimes called “the fat storage hormone.” Every time you eat, insulin is released. Refined carbohydrates and sugar lead to a larger spike in blood glucose and insulin, while eating high-fiber carbohydrates paired with protein and fat don’t cause insulin to spike as much.
When fasting, insulin stays low. Because glucose is not available to be burned for energy, the body can switch to burning fat for energy.
Intermittent fasting and weight loss
If you have extra body fat, losing weight can help you lower your LDL (“bad”) cholesterol, as well as triglycerides and blood sugar. Research shows that while intermittent fasting leads to weight loss, it does not lead to any more weight loss than a calorie deficit overall. To lose weight you need to consume fewer calories than you burn. For some people, the structure of intermittent fasting helps them maintain a calorie deficit.
Intermittent fasting and heart health
Intermittent fasting may lower LDL (“bad”) cholesterol and raise HDL (“good”) cholesterol according to some studies. However, it is difficult to study the effect of intermittent fasting on cholesterol for a few reasons. First, it’s hard to know if the reduced cholesterol is from the weight loss induced by intermittent fasting or from the fasting itself. Some studies show benefits independent of weight loss. Also, many studies to date have studied people who fast for religious reasons, and in general, these populations are healthier to begin with (e.g. many don’t smoke or drink alcohol).
Intermittent fasting is also associated with lower blood pressure, fat loss, and improved blood sugar control.
Should you try intermittent fasting?
Intermittent fasting is not right for everyone, and there are less extreme approaches to having a heart-healthy diet without having to fast. For those with a history of dieting, restricting, and bingeing, intermittent fasting is not the best option. The fasting periods are likely to lead to binges later in the day.
Intermittent fasting is also not a good strategy for those with eating disorders, women who are pregnant or breastfeeding, and those with type 1 diabetes.
Always check with your doctor or dietitian before making dietary changes. And remember, that the most evidence to date on keeping your heart healthy includes eating a Mediterranean-style diet consisting of fruits, vegetables, whole grains, lean proteins, and healthy fats; moving your body daily; keeping stress low; not smoking; and drinking alcohol in moderation. Of course, adding plant stanols to your diet helps too!