There are numerous diets one can use to lose weight. Most of them put an emphasis on what types of foods you should and should not eat.
But did you know there are new weight loss methods that work based on when you eat your food?
Intermittent fasting (if) is a fitness trend that is gradually gaining popularity to help people lose weight and keep it off.
Some studies show that if can also lead to better hormone regulation, reduced inflammation, improved heart health and fat loss. Intermittent fasting may even help you live longer.
This guide will teach you everything you know to help you decide if intermittent fasting is right for you.
What Is Intermittent Fasting?
Intermittent fasting (if) means that you fast (no food intake) for a period of time which can vary from skipping some meals, or fasting for an entire day multiple times a week. The key concept regarding intermittent fasting is not about which foods you should eat, but rather when you should eat them. Intermittent fasting is not necessarily a diet, but rather an eating pattern. When your body is being fed it is digesting and absorbing food, but when you are in a fed state, it is tougher to burn fat since insulin levels are high.
When you finish a meal, the body shifts to a post–absorptive state, in which no food is processed, and can lasts 8 to 12 hours after your last meal. The body is more likely to burn fat in a fasted state since insulin levels are low and you now can burn fat that was inaccessible during the fed state.
Thus, those that begin intermittent fasting are more likely to burn fat without significantly changing what they eat or how much they eat.
Fasting is nothing new. We already do intermittent fasting for 8 hours at night when we are sleeping. In the past humans did intermittent fasting either because food was not available or because of religious reasons.
What Are Some Intermittent Fasting Methods?
There are various ways you can do intermittent fasting; however, they all follow the general principle of following schedule times of fasting.
Here are 5 of the most popular methods you can use to fast.
The leangains method is when you fast for 14 hours (women) to 16 hours (men) each day then eat during the remaining 8-10 hours.
When you fast you cannot consume any calories, however, it is ok to drink black coffee, calorie-free sweeteners, diet soda and sugar-free gum are permitted.
Most people fast during the night then break the fast 6 hours after waking up. This method is popular with many athletes since they time their feeding with when they work out in the afternoon.
You should always consume higher amounts of protein, but on days you exercise you should consume more carbohydrates prior to your workout. Aim to eat more whole, unprocessed foods and consider protein shakes as well .
Pros: For the most part you can consume whatever you want in that 8-10 hours feeding period. However, most already stick to 3 meals since we have been doing that for years.
Cons: Timing of your meals needs to be around your workout to ensure the best results. Also there are restrictions on what you should be eating as well; however, you will see that they are not too strict .
2. Eat Stop Eat
Eat Stop Eat means you fast for 24 hours once or twice per week, but you are allowed to consume calorie-free beverages.
After the fast, resume your regular diet. The idea is that fasting will reduce overall caloric intake for that week without limiting what you eat.
Pros: You can work your way into a 24 hour fast, but first you should adjust and work from 12 hours and move up. Most start this type of fasting when they have a very busy schedule. It is also extremely simple since there is no food restriction on feeding days .
Cons: Fasting 24 hours may be too difficult for people and lead to headaches, fatigue, or cranky mood. Furthermore, fasting this long can lead to binge eating for people.
3. The Warrior Diet
The Warrior Diet consists of “partial fasting” for 20 hours, which should really be referred to as “undereating.”
Throughout the 20 hours you consume a few servings of raw vegetables, fruit, protein shakes, nuts or boiled eggs in small portion.
This undereating is supposed to promote alertness, boost your energy and stimulate fat burning.
However, you main meal is at night in which you eat veggies first, then the protein, and finally the fat [4, 5]. This large meal is supposed to help your body recuperate and repair and grow your muscles.
Only after your finish eating, if you are still hungry do you eat carbohydrates.
Pros: Allows you to eat healthy snacks throughout the 20 hours “partial fasting” so you are not starving. This is easier for many.
Cons: Although you can eat during the “partial fast” there are strict guidelines on what you can eat that cause many to get frustrated. It also can be difficult for those who do not prefer to eat one large meal at night. It can also lead to binge eating.
4. Fat Loss Forever
Fat Loss Forever is a hybrid fasting method that uses many components of intermittent fasting programs such as Leangains, Eat Stop Eat, and The Warrior Diet.
The authors claim that their program gives you a 12 week program to burn faster than ever before, and develop a lifestyle of eating so you can keep those amazing results for a lifetime .
In brief, you follow a specific plan outlined on their website, but the kicker is that you get one cheat a week (to eat whatever you want), followed by a 36 hour fast.
After that cheat day you then go into a cycle that has various different fasting protocols. You fast longest on your busiest days.
The training includes weightlifting programs with free weights and bodyweight to optimize your fat loss.
Pros: There is a unique seven day schedule for fasting with a structured timetable to help you get the most benefits. They also include specific workout programs to complement your fasting protocol for that specific day. Plus, you get one day you can eat whatever you want.
Cons: It can be tough for many to appropriately manage eating healthy for an entire cheat day. Furthermore, this program has a strict seven day fasting/feeding schedule that varies each day that can get confusing to follow and fit into your own busy schedule. Fortunately, the plan does come with a schedule telling you exactly how to fast and exercise for each day.
5. The Alternate-Day Diet
On your “fast” days (“down day”) you typically consume 1/5 of what you normally eat. So if you normally consume 2,000 or 2,500 calories a day, then on a “down” day you would eat only 400-500 calories.
Most people consume meal replacement shakes since they are rich in protein and nutrients that can be sipped throughout the day as opposed to a meal.
Pros: On average, dieters who limit their calorie intake to between 20 percent and 35 percent on Down Days will lose approximately two-and-a-half pounds per week .
Cons: Although this seems simple to follow, it can be easy to binge on a “normal” day since there are fewer restrictions. Your normal days are similar to most days on other diet plans. So if you struggle with healthy eating on a normal day, you should continue to plan your meals ahead of time so that you are not in a position where you are eating junk food.
The Top 3 Health Benefits of Intermittent Fasting
1. Weight Loss
First off, intermittent fasting has been linked to be an effective way for weight loss .
The body stores energy as glycogen and adipose tissue (fat). After all the glycogen stores are full then the energy is stored as fat. Glycogen stores are the first fuel source the body will turn to for energy.
After about 6 to 8 hours we burn through the glycogen supply then use fat for energy. A recent systemic review was published which noted that there is some evidence that there are some beneficial effects on weight loss and reducing cardiovascular risk factors when using intermittent fasting, however, they did urge that there needs to be further randomized trials to learn more about the weight loss outcomes [10, 11].
It should be stressed that the main reason that people are losing weight is because they are consuming fewer calories than they burn. Thus, if you binge during intermittent fasting and consume 5,000 calories when your body normally needs 2,000 calories you are expected to gain weight!
It is stressed that any type of intermittent fasting be combined with weight lifting program to retain your muscle while you burn fat . In fact, intermittent fasting may be a more effective way to retain lean muscle fast during a diet than calorie restriction dieting .
2. Hormonal Balance
Intermittent fasting also regulates the hormones that regulate our metabolism and eating pattern. Insulin is imperative to regulate our blood sugar and fat metabolism.
When you are insulin sensitive that means you secrete enough insulin to get the job done, but not so much that you gain weight and stop burning fat. However, for diabetes, they have insulin resistance and gain a lot of fat .
In fact, fasting combined with exercise is an excellent way to normalize insulin sensitivity .
Leptin is a hormone that regulates fat storage and hunger signals, and ghrelin, another hormone that signals hunger, are both normalized by routine fasting which can lead to weight loss .
There is also evidence that intermittent fasting can increase human growth factor which plays a prominent role in muscular growth and synthesis .
3. Cancer Reduction
Interestingly, studies have also been down to show that intermittent fasting may play a role in cancer reduction.
Animal studies have shown that there is a decrease in lymphoma incidence, longer survival after tumor inoculation, and lower rates of proliferation of several cell types with those that do alternate day fasting [24, 25, 26].
However, the authors caution that more research is required to establish definitively the consequences of fasting on cancer risk. Similarly, another study showed a link that alternate day fasting may even prolong our lives and reduce our resistance to infection [27, 28].
Who Should Avoid Intermittent Fasting?
If you are underweight or have an eating disorder, you should not start intermittent fasting until you discuss this with a healthcare professional.
It can be harmful for you to fast since you are already underweight and need to gain weight. Furthermore, if you have an eating disorder, fasting can further exacerbate your unhealthy relationship with food.
Women should be careful with intermittent fasting since there can be some physiological effects due to hormone changes.
Although there are not any significant human trials showing this, there are occasionally some stories of women missing their periods during intermittent fasting and then resumed their periods when they stopped intermittent fasting.
If you are trying to get pregnant, it is best to avoid intermittent fasting at this time.
Also, if you find that you binge eat a lot after periods of hunger, it is probably best to avoid fasting for an extended period of time. Perhaps you should stick to a calorie restriction diet so that you can eat more frequently without binge eating.
However, if you are insistent to try fasting, then slowly see how your body responds to fasting for a few hours a day then slowly increase the time frame.
See how your body responds and what your habits are. You may find that eventually you can do a 16-24 hour fast without binge eating.
Also if you are a diabetic that takes insulin, you must discuss intermittent fasting with your doctor because if you take too much insulin when you are not eating you can cause a hypoglycemic crisis (low blood sugar) that can result in seizures, confusion, coma and even death.
Intermittent Fasting Common Side Effects
The number one side effect you will experience will be hunger. This is no surprise, but rest assured, as you go through the intermittent fasting cycle your body will get acclimated to it and you will get less hungry.
You may also feel fatigue and crankiness from lack of energy. At times you may lose focus since your brain is in need of energy.
Remember, this is normal since you are on a new eating pattern. Your body will adjust.
However, if you have chronic medical conditions, it is imperative that you discuss starting intermittent fasting with your diet before starting. Patients at risk include those with diabetes (especially those that are dependent on insulin), low blood sugar, underweight, eating disorders, female with amenorrhea (absence of periods), pregnant, breastfeeding, females actively trying to conceive.
In general, intermittent fasting is safe; however, these groups can be affected and are advised to discuss with their doctor how this type of diet can affect them given their conditions.
Intermittent Fasting faqs
1. Can I drink during my fasting period?
Yes! You are encouraged to drink plenty of water, black coffee, tea, and non-caloric beverages.
However, do not add sugar or milk to your coffee. This is important because you need fluid to stay hydrated.
2. Isn’t breakfast the most important meal of the day?
It’s ok to skip on this fast. Remember, you are giving yourself time to burn fat.
3. Can I take supplements?
Yes! It is highly encouraged you take whey protein powder to see greater muscle gains.
Furthermore, you should consider Creatine to add on muscle size while you are dieting down.
4. What can I do to get more energy for my workouts?
During periods when you are allowed to eat, you will see that most diets time your heavier meals before you workouts you have energy.
If you do workout during the fasting part of your day consider drinking coffee before your workout or have a pre-workout energy drink.
5. Will I lose muscle mass?
During any diet you are at risk of losing muscle since you are burning calories. This is why it is critical to consume high protein and lift weights to retain as much muscle as possible .
Studies have shown that intermittent fasting may be a more effective way to retain lean muscle fast during a diet than calorie restriction dieting .
6. Can my child fast?
This is not advised since children need calories to ensure natural growth and to safely allow them to reach their puberty milestones.
7. How do I fit intermittent fasting into my schedule?
If you know you are going to be working and be very busy, it may be best to fast during those extended times of work, this way you can be actively engaged without worrying about food.
8. Does this complicate my life?
Most people find that fasting makes life so much easier since they are focused on eating only when they are allowed to eat.
They find that after a few weeks of adjustment they have greater energy, elevated mood, and greater self-esteem since they see the results quickly.
9. Can I do cardio?
Yes! Cardio will enhance your weight loss, but remember to continue weightlifting and a high protein diet to retain as much muscle as possible.
10. What if I get so hungry I eat something?
Then eat something. It’s ok. Slowly build up your tolerance with fasting.
If you fail at 12 hours, then try 8 hours and give your body time to adjust. As you adjust you can extend the fasting time and see greater results.
Should I Try Intermittent Fasting?
Look, no one needs to do intermittent fasting. There has been incredible success with those that do calorie restriction diets combined with exercise.
However, if you want to try something new then go for it. As for me, I am going to try it this month!
I will be working four weeks straight in the icu working from 7pm to 7am and during these nights they can be crazy with multiple cardiac arrests and new admissions for those on ventilators.
The cafeteria is closed, and I am never sure when I am going to get my next meal. Even when I bring my meals to work on night shift, it gets so busy I can’t really eat anyway. So, I accepted this fact and am going to tailor my eating pattern around the madness.
I will wake up at 5pm to get ready for work and drink a protein shake and head to the hospital. Then I will fast for 12 hours.
After that shift I will head to the gym with another pre-workout drink and protein shake and get my weight lifting and cardio in. After that I will eat a normal protein rich diet and go back to bed.
My eating pattern is a little bit of a combination of the options I described in the article; however, I will try it and see how it works for me.
Again, this is what I feel will work for me based on my new sleeping pattern and work schedule. Do I feel this will work? Yes.
Previously on night shift I always found myself so busy that I was not even thinking about food, and when I did get downtime I ate food I brought from home. Thus, fasting for 12 hours at work makes sense for me to try this time.
I have tried fasting a little before in the past, however, never to the extent of doing it for four consecutive weeks while working full-time.
Given the strong research behind intermittent fasting, I am confident I will be leaner and more ripped in four short weeks! So what are you waiting for? Let’s give it a try together!
Rajiv M Mallipudi, md, mhs is an internal medicine resident physician, personal trainer, athlete and author. He has over a decade of personal training experience and helped hundreds of clients of all levels achieve their weight loss and fitness goals. This inspired him to work as a clinical researcher at the nationally recognized Johns Hopkins Hospital Weight Management Center. During medical school he and his classmates created the health and wellness organization, medfit, which provided personal training and nutrition counseling to the medical student body. In his spare time, Dr. Mallipudi enjoys playing ice hockey, dancing, and training for his next bodybuilding and powerlifting competitions. Dr. Mallipudi serves as a contributing writer for the Diet and Fitness sections.
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