Recently, while catching up with friends, we were discussing diet trends. Five years ago, I learned about juicing, four years ago about the paleo diet, two years ago about boot camps, and a year ago about keto. This year I learned about intermittent fasting for weight loss. My friends were not the first people that I have known to follow intermittent fasting, but I was intrigued to understand more about why they followed this particular diet and why one friend claimed that this is the best diet ever because he is not restricting any foods. I always find these conversations enlightening. I learn about how diet information travels and how people interpret what is healthy and what is not.
Healthy is a debatable term, just like defining success. Your doctor can give you a clean bill of health following medical tests, but there is so much that we don’t know, which is why your doctor cannot tell you what diet is best for you. Even amongst dietitians and nutritionists, there is a variance in the interpretation of a healthy diet. Healthy is relative to each person.
So, back to this year’s diet conversation. When I think of fasting, I think of Yom Kippur, the day of atonement in the Jewish religion. I have been fasting one day a year for the last 32 years, and it gets harder each year. I don’t feel great, I am dehydrated, and I feel ill. When I fast for 24 hours, I learn to appreciate food. The fasting day culminates with a festive meal after which makes me feel even sicker from overeating. So, why would someone want to subject themselves regularly to fasting?
I decided to check emerging research on intermittent fasting and its health benefits in contrast to the traditional calorie reducing diets for weight loss.
What is Intermittent Fasting?
Intermittent fasting is simply recurrent or periodic fasting. It’s an “eating pattern,” rather than a “diet.” It focuses on regularly reducing food and liquid intake during pre-set times. It’s controlling when you eat and drink, as opposed to what you eat and drink.
The research is relatively new, and the results to date are very promising.
Intermittent fasting has a few advantages over regular calorie-reduced diets. Not only is it more comfortable for many people to stick with, but it also seems to have power over how our body uses our food for fuel. These are excellent things when it comes to long-term health.
Calorie Restricted Diets vs Intermittent Fasting for Weight Loss
Weight loss diets typically impose restrictions on food intake and portion sizes. By consistently reducing the amount of food ingested by 15-60%, overweight and obese individuals lose weight and fat. This is called “continuous” calorie reduction because one is repeatedly reducing what is ingested – at every meal and snack, every day. Calorie-reduced diets can include eating smaller servings, low-calorie substitutions, and/or cutting out some snacks/desserts every day.
Intermittent fasting does not regulate what you eat or how much you eat, but rather the timing of when you eat. Following intermittent fasting, allows you to eat what you want, but only during certain times.
Both continuous calorie reduction and intermittent fasting have shown to have similar weight loss results. But, there are a few key benefits of intermittent fasting over typical calorie reducing diets.
The Benefits of Intermittent Fasting
For people who have excess weight to lose, health benefits have been seen with a loss of about 5-6% of a person’s body weight. Health benefits included lower blood lipids (LDL cholesterol and triglycerides), better blood sugar management (lower glucose and insulin), lower blood pressure, and lower levels of inflammation (C-reactive protein).
For my friend, the benefits of intermittent fasting came after years of trying to fit the mould of typical weight loss diets or counting calories. He much preferred intermittent fasting because he could experience weight loss without guilt.
Numerous studies prove what we know already: it’s challenging to sustain a (continuous) calorie-reduced diet for a long time. This is the reason why many people prefer intermittent fasting – it gets similar weight and fat loss results, but it’s easier for many people to stick with.
Other advantages to intermittent fasting over calorie-reduced diets are that it can help people eat more intentionally (and less mindlessly).
Also, some studies show that intermittent fasting makes our metabolism more flexible so it can preferentially burn fat while preserving the muscles. This is a great benefit because that can help improve body composition in people with excess weight.
But, before you run off and start intermittent fasting, there are important things to consider.
Who Should NOT try Intermittent Fasting?
I have outlined above some of the health benefits that can be achieved with intermittent fasting, but before you try it, I recommend that you check with your healthcare provider to determine if it is suitable for you.
Intermittent fasting can provide you with many health benefits, but there are a few adverse effects have been reported as well. Before starting, you should consider: bad temper, low mood, lack of concentration, feeling cold, nausea, vomiting, constipation, swelling, hair loss, muscle weakness, uric acid in the blood and reduced kidney function, menstrual irregularities, abnormal liver function tests, headaches, fainting, weakness, dehydration, mild metabolic acidosis, preoccupation with food, erratic eating patterns, binging, and hunger pangs.
If done too often or for too many days, intermittent fasting can have more serious effects. Excessive fasting can lead to malnutrition (including vitamin B1 deficiency), decreased bone density, eating disorders, susceptibility to infectious diseases, or moderate damage to organs.
How Long Should I Fast?
There are many ways to intermittently fast. The different methods offer different health effects for people with different health goals.
Here are a few different Intermittent fasting patterns documented:
- Alternate-day fasting (ADF) – One day of fasting, one day of “feasting.” Continue fasting on alternate days.
- Alternate-day modified fasting (ADMF) – Eat 25-40% of your daily needs one day, then eat normally the next. Continue alternating days.
- Periodic fasting (PF) or “Two day” fasting – Each week has 1 or 2 days to eat very few calories per day (e.g. 0-880 cal/day). The other five days you eat normally. Example: 5:2 diet, where you eat no more than 500 calories/day for two non-consecutive days each week.
- Time-restricted fasting (TRF) – Fast for 12-16 hours every day and eat normally during the other 8-12 hours.
- One 24-hour period of fasting each month.
Several researchers suggest that the alternate-day modified (ADMF) fasting is preferable because it is likely the easiest to follow and may cause the least amount of stress on the body and mind.
You may be wondering if fasting intermittently increases what you eat during those times when you do eat. And that’s a great question.
The interesting thing is, it seems not to!
Studies show that alternate-day fasting reduces overall calorie intake. Plus, on the non-restricted days, some people naturally reduce their energy intake by up to 20-30%. This means another side benefit of intermittent fasting is that it can help reduce food costs too!
Keep in mind that reducing your food intake also reduces your nutrient intake. It’s important to ensure you get enough essential nutrients for long-term health.
Is Intermittent Fasting Right For You?
Intermittent fasting is a way to get the benefits of a regular calorie-reduced diet without restricting what you eat, just when you eat it. Intermittent fasting reduces both weight and fat and can improve blood sugar and blood lipids. It has also been shown to lower blood pressure and some markers of inflammation. Losing weight and excess fat reduces the risk of diabetes, improves health, and increases the function of both the body and mind.
While some of the benefits of intermittent fasting are similar to those with calorie-reduced diets, intermittent fasting has some key advantages including being easier for some people to stick with and it might help people eat more intentionally.
If you want to know more about safely following an intermittent fasting meal plan, contact me, and remember, don’t start a new diet or eating pattern before discussing it with your healthcare provider.