Intermittent fasting is a popular weight-loss method that many studies have shown to be effective. When combined with regular exercise, intermittent fasting can help people reach their target weight.
As its name suggests, intermittent fasting consists of eating within specified periods of time. Unlike other weight-loss programs, intermittent fasting does not specify which foods you can eat. Rather, it specifies when you may eat them. Some forms of intermittent fasting permit you to eat every day, but only between certain hours. Others require you to eat nothing (or very little) for an entire day, although never for two days in a row.
It is important to understand that this type of weight-loss program is not one size fits all. Different body types respond to different fasting plans. So, it is important to identify what your body type is in order to achieve the most benefit from your new eating pattern.
How it works
Although intermittent fasting is very popular in the health and fitness communities, this eating plan doesn’t address all the problems caused by a sedentary lifestyle or eating unhealthy food. But it can potentially produce health benefits, including weight loss, by causing a metabolic switch.
Normally, the body gets energy from glucose, which comes from the food and beverages we eat and drink. When you go for more than 12 hours without eating, however, the glucose level in your blood drops to the point that your body needs to use your fat stores for energy. By breaking down fat into chemicals called ketones, the body can then use the ketones for energy.
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Using ketones for energy is called ketosis, and changing to this way of producing energy is the metabolic switch. Using this type of energy burn is more efficient for the body, and it’s how intermittent fasting helps you lose weight.
In addition to weight loss, intermittent fasting may also improve the health of people with certain conditions such as type 2 diabetes, heart disease, seizures, and other conditions affecting the brain. It may even improve overall cognitive function, delay aging, and reduce inflammation.
Time-restricted eating
The intermittent fasting methods in which you only eat during a certain time each day are called time-restricted eating. One of their major benefits is that most of the time in which you can’t eat occurs when you’re sleeping.
Two popular time-restricted eating approaches are 16/8 and 14/10. With the 16/8 method, you can only eat within an eight-hour period, such as from noon to 8 p.m. The 14/10 method allows you to eat within a 10-hour period.
Another type of time-restricted eating is the Warrior Diet. With this method, you can only eat a small amount of fruits and vegetables during the day, and then eat one large meal at night.
Low-to-no calorie days
The other popular intermittent fasting methods require you to eat nothing or very little for entire days.
• In Alternate Day Fasting, you alternate between days on which you can eat whatever you like and days on which you can only eat 500 calories or less.
• The Eat-Stop-Eat method requires you to fast for 24 hours once or twice a week.
• The 5:2 diet requires you to consume only 500 to 600 calories on two nonconsecutive days while allowing you to eat normally the other five days.
Choosing the right intermittent fasting strategy
Your individual metabolism affects how your body responds to food intake and how your body creates needed energy. Knowing your unique body metabolism is the key to creating the metabolic switch and achieving your desired weight loss.
• Endomorphs have a slow metabolism, gain weight easily, and have trouble losing it. The ideal intermittent fasting approach for this body type would be either the one-meal-a-day approach or alternate-day fasting.
• Ectomorphs have a fast metabolism, tend to be thin, and struggle to gain both weight and muscle. For ectomorphs, weight loss is not the goal, but rather the other health benefits of intermittent fasting. So people with this body type should consider fasting for at most 12 – 14 hours per day, with maybe a 24-hour fast once every few weeks.
• Mesomorphs are somewhere in between. They tend to build muscle easily and are usually neither underweight nor overweight. People with this body type may want to experiment with moderate intermittent fasting approaches such as fasting 18 – 20 hours a day, four or five times a week.
What studies say about intermittent fasting
Studies of intermittent fasting generally have shown it to be effective. A review of animal and human studies on intermittent fasting published in The New England Journal of Medicine suggests it can help with weight loss, reduce blood pressure, and increase longevity.
In an article published in Endocrine Reviews, researchers said that eating only within an eight-to-10 hour window each day can help prevent and manage such chronic conditions as diabetes and heart disease.
However, a study published in the Journal of the American Heart Association found that how frequently, and how much, people ate had a greater effect on their weight than when they ate. And another study published in the medical journal, JAMA Internal Medicine, found that intermittent fasting didn’t cause participants to lose a significant amount of weight, but did cause them to lose lean muscle.
What to consider
If you want to lose weight, and think intermittent fasting could be beneficial in helping you reach your personal weight-loss goals, it may be worth considering. Before making any changes to your diet or eating schedule, be sure to consult with your primary care provider to make sure it is a safe and healthy plan for your lifestyle.