How Intermittent Fasting Works
Intermittent fasting doesnt promote weight loss only because it creates a calorie deficit. Intermittent fasting also induces a metabolic change. What is the metabolic change I am referring to? Its your body switching over to fat burning from glucose burning. If you fast long enough, your body will run out of glycogen, and start producing ketones from your fat cells to use for energy. This is how you can be in ketosis without being on the keto diet.
What’s The Evidence From Animal Studies
More animal research has been done on calorie restriction than on fasting. In some experiments, calorie restriction is also a form of fasting because the lab animals consume all their daily allotted food within hours and go many more hours without any food.
In these studies, when rodents and other animals were given 10 percent to 40 percent fewer calories than usual but provided with all necessary nutrients, many showed extension of lifespan and reduced rates of several diseases, especially cancers. But, some studies did not show this benefit, and in some mouse strains, calorie restriction shortened lifespan rather than extending it.
In the worm C. elegans, a fasting diet increased lifespan by 40 percent. A study with fruit flies found that calorie restrictionbut not intermittent fastingwas associated with living longer. One study of male mice found that lifelong alternate-day fasting increased longevity, mainly by delaying cancer occurrence rather than slowing other aging processes.
What Occurs When A Person Develops Insulin Resistance
The impact on insulin and insulin resistance, however, was the most significant aspect of the research. Finally, obesity and weight increase are linked to hyperinsulinemia and insulin resistance.
Harvie3fasting improves insulin levels and insulin resistance in a clear and substantial way. In the CRaP group, there was no improvement in insulin resistance , which leads to increased insulin levels in a vicious cycle. This maintains a high goal weight and avoids long-term weight loss.
For thousands of years, fasting has been shown to be helpful in the battle against obesity. Only in the past 50 years has portion control been utilized successfully. Experts like Dr. Katz and others, on the other hand, are continually urging us to consume less calories in books, on TV, and on the Internet. Isnt it true that they dont believe weve tried? Is it possible that theyre making fun of us?
Fasting, the only really successful technique, is frequently dismissed as a hazardous habit similar to adoration and voodoo. Most diets fail to take into account the biological concept of homeostasis, which refers to the bodys capacity to adjust to changing environmental circumstances. Your body will adjust if you attempt to maintain a consistent diet. This implies that effective dieting requires an intermittent rather than a continuous approach. This is a significant distinction.
Jason Fung, Ph.D.
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Intermittent Fasting For Weight Loss: What The Science Says
ByLou Mudgepublished 19 August 22
Here’s what evidence says about the efficacy and safety of different styles of intermittent fasting for weight loss
Intermittent fasting for weight loss can be an effective way to lose unwanted fat, particularly in those with obesity and metabolic syndrome. Multiple studies have found that the metabolic impact of intermittent fasting, coupled with the calorie deficit that it tends to generate, can help to create a downward trend on the scales.
There are different styles of intermittent fasting, so if you’re looking to embark on this approach it’s important find the right eating pattern for you. Whether its a more extreme form like the 5:2 diet, or a gentler approach such as 16: 8 intermittent fasting, intermittent fasting should be sustainable and fit with your lifestyle.
In this article, we’ll break down the science behind intermittent fasting for weight loss, and which approaches are most effective. Plus, we’ve spoken to experts in cardiometabolic health and oncology about the best ways to lose weight sustainably and safely through intermittent fasting. Remember, it’s best to consult a qualified medical professional or registered dietitian if you are considering making significant changes to your diet.
Fasting Can Help You Lose Weight
Between 2015 and 2018, researchers in the UK found 36 slim, healthy people to take part in the study. For four weeks, they kept track of what they ate and how much they moved around. The participants were then put into one of three groups of 12 people.
The first group, the “energy restriction” group, only used 75% of the energy they usually use in a day.
The second group lost weight by fasting and cutting back on calories. On some days, they didn’t eat anything, and on other days, they ate 150% of their normal calorie intake.
The third group did not have any energy limits put on it. On some days, they didn’t eat anything, and on other days, they ate 200 percent more calories than they normally would.
During their fasting periods, the people in the fasting groups didn’t eat any foods that give them energy. This made sure that their diet changes were consistent and that their bodies’ systems related to fasting were turned on.
A bunch of lab tests were done on the people before and after the 3-week intervention. The researchers also kept track of what the participants ate and how much exercise they did. They also took samples of fat tissue from some of them.
At the end of the study, people on low-calorie diets had lost an average of 1.91 kg . People who fasted and limited their calories lost an average of 1.60 kg, while those who didn’t limit their calories only lost 0.52 kg.
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Why 3 Pm Is A Key Time To Start Eating Less Food
Peeke also recommended that I stick to having lunch be my biggest meal of the day. Theres a study that a majority of Americans eat over the course of 15 to 16 hours out of the day, with the majority of their calories coming after 3 p.m. Its a recipe for disaster, she says, referencing a study published in November 2015 in Cell Metabolism.
Peeke suggested that rather than having my banana protein shake as an evening dessert and not eating anything before exercising, I instead drink it first thing in the morning. This way, the carbs from the banana would give me an instant source of energy to fuel my workout and my body would be processing the carbohydrates at an optimal time of the day.
The switch immediately paid dividends. I had way more energy throughout my workout. Because my body was working at a higher intensity, I was burning more calories than I would be even if Id been doing fasted cardio. Peeke recommended that I try to stay under a 12-hour window of restricted eating, but I was able to manage my dinnertime to keep my eating in a 10-hour window. Although my weight drifted up by 2 lb, it was because I was adding muscle mass instead of fat. The additional muscle in my arms and shoulders were noticeable. And as my body fat percentage got lower, I started to see some veins popping out of my biceps, forearms, and calves.
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What Foods Can I Eat And What Do I Have To Avoid
This is a huge perk of intermittent fasting: You technically dont have to alter what you eatyou just have to eat within a certain window of time. On an intermittent fasting diet you dont need to avoid any foods, Gans says. However, one should focus on consuming foods that are high in fiber and healthy fats for satiety, such as quinoa, black beans, spinach, strawberries, avocado, and almonds, and of course other nutrient-dense foods for overall health.
At the same time, its a good idea to limit sugary drinks, processed foods, and simple carbs like white bread, advises Cording. Theyre not providing you with much nourishment, she says. You really want to focus on foods that do you a favor.
That said, plenty of people have paired intermittent fasting with another type of diet, like keto. Again, its not a requirement, but doing intermittent fasting while also altering your diet could help you get results faster.
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How To Get Started With Intermittent Fasting
There are several types of intermittent fasting you can follow:
- The 16/8 or Leangains Method: Fast for 16 hours per day and eat in the remaining 8-hour window. Most people will skip breakfast and eat from 1pm to 9pm for example.
- The 5:2 Diet: Eat normally for 5 days of the week, but only eat up to 600 calories on the other two days.
- Eat-Stop-Eat or Spontaneous Fasting: Fast for a 12 or 24 hour period multiple times per week. There is no real schedule for this one.
- Alternate Day Fasting: Fast for one day and eat normally the next day. Continue to alternate days of fasting and normal eating.
You can view a more detailed description of each type here.
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Calorie Restriction And Fasting Diets: What Do We Know
You may have heard about calorie restriction and fasting diets and wondered why they’re getting so much attention in the news. Aren’t they just other terms for ?
No, they’re not. Calorie restriction means reducing average daily caloric intake below what is typical or habitual, without malnutrition or deprivation of . In a fasting diet, a person does not eat at all or severely limits intake during certain times of the day, week, or month. A practical effect of a fasting diet may be fewer calories because there is less time for regular eating.
These eating patterns are being studied as possible ways to maintain good health and live longer. They are not temporary weight-loss plans. Interest in their potential health and aging benefits stems from decades of research with a variety of animals, including worms, crabs, snails, fruit flies, and rodents. In many experiments, calorie-restricted feeding delayed the onset of age-related disorders and, in some studies, extended lifespan.
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Science Investigates: Fasting Vs Calorie Restriction
People are always on the lookout for quick and easy ways to lose weight, which is why there are approximately 5 billion new diet books written every year thats our unscientific, but probably not inaccurate, estimate. Speaking of unscientific, the problem with the plans in these books is their so-called new approaches to weight loss havent been tested, well, scientifically. And when they get scientists to pay attention, the plans often fail to produce the stellar results they claim.
One weight-loss method thats gotten a lot of attention lately is fasting, where people go without eating for several hours or even a full day. Search the internet and Reddit boards, and youll find passionate devotees talking about the advantages of fasting for weight loss, muscle gain and other benefits, like improved mental clarity. And while there is research to back up some of these claims, much of it is preliminary or was conducted on animals.
Lately, researchers have been looking into fasting more deeply and are starting to fill this knowledge void. A study published this May in the Journal of the American Medical Association: Internal Medicinesought to find out whether fasting was any better or worse at helping people lose weight than a more traditional diet. Heres what they discovered:
WHAT DID THE STUDY EXAMINE?
The study looked at the effectiveness of two diets:
WHO TOOK PART IN THE STUDY?
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HOW LONG DID THE STUDY LAST?
Is Intermittent Fasting Healthy
Research has indicated there may be health benefits connected to intermittent fasting, although some studies were done on animals only and more research is needed. A review of various studies indicated that intermittent fasting may improve factors related to obesity and heart health, such as body mass index , blood pressure, bad cholesterol and fasting blood sugar. However, benefits may only be short-term and appear to level off by about 6 months, either because the body adapts or people cant stick to the eating plan.
Some people may find it hard to maintain any diet or new eating program for longer than four to six months, so adapting the basics of eating healthy and staying physically active is the ultimate goal, Cole said.
Although intermittent fasting may provide weight loss and other health benefits, there are certain people who should not follow this eating method, including women who are pregnant or breastfeeding, people with diabetes and those with a history of eating disorders. Its also not appropriate for people under age 18.
Even if you dont fall into one of these groups, its best to talk with your doctor before trying this or any diet because it may be dangerous if you have certain health conditions or take specific medications.
FirstHealths Diabetes & Nutrition Education Center offers counseling for individuals with specific medical needs as well as those who wish to maintain optimal health. To schedule an appointment or learn more, call 715-1925.
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Which Approach Is Right For You
They might seem similar, but CR and IF have crucial differences. Since IF is typically easier to maintain both psychologically and physically, its often more successful at helping to regulate glucose, control lipids, manage body weight, boost lean mass, and reduce the risk of chronic diseases. However, its not recommended for pregnant women, people with histories of eating disorders, or the chronically stressed.
CR works well for weight loss in the short term, but it can be tough to be consistent long enough to see results and could lead to malnutrition if done incorrectly. Because CR is spread out over many lower-calorie, less-satiating meals, it can make you hungrier, unmotivated, irritable, and tired which can trick your brain into craving unhealthy foods. CR also doesnt address the problem of insulin resistance.
No matter what approach you take or your reasoning behind it, always focus on eating healthy, nourishing foods.
If you need help planning or preparing meals, consider using a meal delivery service that specializes in IF, CR, and other meal plans tailored to your specific goals.
Kelley Baker is a Nutrition Health Coach with 15 years of experience of personal training and holistic lifestyle coaching. Her certifications include NASM, C.H.E.K, ICANS, and Poliquin.
What Is Calorie Restriction
Calorie restriction is an umbrella term. Lets break it into two chunks:
If you have body fat to lose, a mild calorie deficit of 5-20% per day can be a sustainable way to lose it. This mild energy deficit is generally the kind promoted by IF.
Chronic calorie restriction, on the other hand, refers to a chronically insufficient dietusually 20-50% fewer calories per day than your metabolism demands. This is starvation.
If youve ever watched History Channels hit show Alone, youre witnessing starvation up close. In the show, contestants try to outlast one another in brutal environments , and never get enough to eat.
Everybody loses weight on Alone, much of it from muscle. No surprise there.
If you havent seen Alone, you might have watched The Biggest Losera show in which severe calorie restriction spurs rapid and significant weight loss in overweight participants. And it works, at least while the cameras are rolling.
But when the contestants return home and resume normal eating patterns, they invariably regain the lost weight. Why? Because their metabolisms have permanently slowed down, even beyond what would be predicted by weight loss. In other words, they burn fewer calories at rest. Not ideal for weight loss maintenance.
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What Are The Benefits Of The : 2 Diet
According to Ly, a study in the Clinical Nutrition Journal found the 5:2 diet to be a safe and effective protocol for weight loss. It has generally been accepted by researchers as easy to follow too.
Adding in additional factors for dieters, such as group support, increased adherence and impact, research in PLOS One found.
While there arent many studies specifically on the 5:2 diet, research into intermittent fasting has revealed some great health benefits. These include changes in body composition, fat loss, improved heart health and lowered blood sugar levels.
One study published in the Canadian Family Physician journal found that intermittent fasting could aid weight loss in a similar way to calorie restriction, and it could also help to reduce cholesterol.
Research in the Journal of the Academy of Nutrition and Dietetics that looked into the health benefits of alternate day fasting, which is similar to the 5:2 diet, found it could reduce insulin resistance, asthma and even menopausal hot flushes.
Fasting can increase innate healing mechanisms in the body such as autophagy, which is where your body cleans out old and damaged cells, says Carolyn Nicholas, functional medicine certified health coach and director of Health Coaching app Able. Fasting can also help you to become metabolically flexible, basically switching between burning glucose or ketones for fuel.
Fasting On A Regular Basis
The hormonal changes that occur during IF are very different, as we described in depth in our 27-part series on fasting. During fasting, hunger reduces and TEE rises, in contrast to the CRaP. The body is attempting to shed pounds and is assisting you in this endeavor. Whats more, it addresses the long-term issue of insulin resistance. You wont receive any of the positive hormonal changes of fasting by just cutting calories.
Insulin resistance is avoided during IF due to the intermittent nature of the treatment. CRaP and IF were compared in a recent research titled Effect of periodic or continuous energy restriction on weight reduction and indicators of metabolic disease risk: a randomized trial in overweight young women. 107 women were randomly allocated to one of two methods in this research. The first was a 25 percent continuous energy restriction , which was comparable to the CRaP portion control method. The second approach was to reduce energy use intermittently . Patients were permitted to eat normally five days a week but just 25% of their regular calories two days a week, similar to Dr. Michael Mosleys 5:2 diet.
What were the outcomes six months later? There was no substantial difference in terms of weight and fat reduction, but fasting was better .