Losing weight is hard work.
But it’s not necessarily complicated.
“Eat less and move more” is the simple mantra of many weight loss coaches.
But the “eat less” portion of dieting is always under new scrutiny as researchers and doctors look for ways to help people adapt to that part of the weight loss equation.
Fasting has gained a lot of attention in recent years. In particular, the idea of “alternate day fasting” is gaining traction.
People who hate the sound of a conventional diet — eating a set number of calories each day and having to exercise to “earn” more — might like the idea of eating little on some days and a lot more on others.
However, the big question is, “Does this diet regimen work?”
What the research concluded
The concept behind alternate day fasting (ADF) is simple.
It requires you to fast every other day.
On fasting days, you eat 25 percent of your calorie needs. For most people, that’s 500 to 600 calories.
On “feast” days or nonfasting days, you either don’t have a goal, or you eat 125 percent of your calorie needs. That equals about 2,500 calories.
A recently published study suggests that this type of fasting diet may help people lose weight, but it’s not more effective than traditional calorie restrictive dieting.
During the year-long study, participants were asked to either follow an ADF plan or restrict daily calories. A third group didn’t change their previous eating patterns.
After one year, both the ADF group and the calorie-counting group had lost about 13 pounds. Researchers said the fasting group did not have improved cholesterol levels or overall cardiovascular health by the end of the study.
The reason the results were similar between the ADF group and the calorie-counting groups has to do with your metabolism, says Dr. John Salerno, a New York-based family physician and author of “Fight Fat with Fat.”
“With fasting, the longer you do it, the more you slow down your metabolism. With calorie restriction, you are doing the same thing, lowering your metabolism,” Salerno told Healthline. “With alternate day fasting, you are more than likely taking in the same amount of calories over a two-day period, and your metabolism is around the same.”
The researchers also reported that more members of the ADF group dropped out of the study. These participants stated following an ADF plan was too difficult and not sustainable for them.
Additionally, the researchers noted that most people in the ADF group ate more than their limit on fasting days (500 calories) and ate less than their allotment on feasting days (2,500 calories).
However, the study participants were not allowed to pick their plan prior to beginning the study.
It’s possible, the researchers said, that people might have been more successful if they’d been able to select the type of diet they’d be following.
The science behind fasting
By definition, fasting is going without food or drink for a specified period of time.
Fasting is often done for religious reasons, such as to observe periods of mourning or meditation.
Recently, however, fasting has been adopted by dieters. Some promote fasting to lose weight. Others use fasting to help them “reset” their eating habits, especially after a period of indulgence.
The idea behind fasting is simple: If you reduce how many calories you eat, you will lose weight. The practice of fasting is a bit more involved, however.
During a period of fasting, you greatly restrict what you eat. In some cases, you eat nothing. You are allowed to drink zero-calorie beverages. If you do eat during that time, you eat very little.
On nonfasting days, most people eat with few restrictions. Many fasters will not follow any set calorie goal. Others might have a goal that allows them to eat slightly more than they’d eat on an average day.
Other types of fasting
Fasting isn’t always one-size-fits all.
It’s important you find the type of fasting that is right for you. A technique that fits your lifestyle and your goals may help you be more successful.
Intermittent fasting is the most common type of fasting for weight loss. This dieting pattern involves some days of restricted eating followed by days of unrestricted eating.
Besides alternate day fasting, there are several other types of intermittent fasting.
The 5:2 Fast
The 5:2 fast requires you to eat normally for five days of the week.
The other two days you greatly restrict your calories. For most people, that means eating only 500 calories per day.
The 16/8 Fast
For this method, you will fast for 16 hours each day. During the other eight hours, you’re allowed to eat. For many people, this means not eating after dinner and then skipping breakfast each morning.
Shayla Ridore has been practicing this type of fasting for two months.
“I work overnight hours at the moment, and I typically stop eating around 11 p.m. or 12 a.m., and can eat again at 3 p.m. or 4 p.m. the next day,” she told Healthline. “The fasting schedule is flexible so as long as I hit 16 hours it doesn’t really matter what the hours are.”
Ridore, who is an accountant coordinator with a public relations firm, uses fasting to lose weight.
“I was trying to lose weight before I started fasting and was just not seeing any real results,” she said. “I decided to try it to switch up what I was doing since it wasn’t really working for me. I loved it immediately. I started to lose the weight I hadn’t been able to lose before. I saw results pretty quickly, too.”
This type of fasting method requires fasting for longer periods of time, one to two times per week.
Most fast periods begin after dinner one day and go until the next dinner time. During the long fast, you may drink water, coffee, or other zero-calorie beverages.
Some people have created a personal timeline using the same method.
For example, Geoff Woo fasts 36 hours every week, from Monday night after dinner to Wednesday morning for breakfast.
“I do this to enhance my productivity and jumpstart processes like neurogenesis, the growth of new neurons,” he told Healthline.
Woo, who is the chief executive officer of Nootrobox, and organizer for WeFast Intermittent Fasting Community, says fasting is more effective than other weight loss methods.
“Fasting is sustainable over long periods of time because it has built-in periods of intensity and relaxation. I know I can be disciplined for short bursts of time,” he said. “Being disciplined for the rest of your life with types of foods and number of calories is so much more complicated. Too many rules. Fasting is simple.”
Complications of fasting
Like any weight loss technique, fasting is not without its detractors and potential problems.
“The main danger to alternate day fasting or any fasting is becoming hypoglycemic [low blood sugar],” Dr. Monali Y. Desai, a cardiologist in New York, told Healthline. “It will also change the way some medications are absorbed in your body. If you have any preexisting medical conditions such as diabetes, or take any prescription medications, you should check with your doctor first before starting alternate day fasting.”
Salerno recommends you begin any fast under medical supervision.
“Medications would have to be reduced, especially if someone is on insulin or diabetic medications,” he said. “There are a lot of potential detriments if they’re not being followed closely.”
If you’re considering fasting as a way to lose weight or looking for something to shake up your current weight loss plan, talk with your doctor.
Your doctor may be able to help prepare you for a fasting period with helpful information and tools. Your doctor can also help you be alert for potential problems with your fasting method.
“People should just try it with an open mind and give it at least a week before deciding if it’s for you or not,” Ridore said. “Anyone looking to begin fasting should know that there will be times that they will feel hungry, but never a painful hungry.”
The bottom line, Salerno says, is to not expect dramatic results quickly. Weight loss takes time and dedication.
“It’s never a quick fix. If it’s slow and steady, it can be more easily maintained,” he said. “You never want to lose weight too quickly because the body will turn off its metabolism, and you will see a big spike in gain if you go back to eating a normal amount of calories.”