In Part 1 of this discussion about fasting, we looked at how fasting might affect certain health conditions and why fasting, unlike dieting or just reducing calories, has a unique impact on your physiology. But there's more to a fasting program than simply not eating.
Types of fasts
Current popular fasts include:
The Fast Diet: Eat whatever you want for five days, then fast for two days (originated in Britain). Jimmy Kimmel credits the "5:2 Diet" with helping him to finally lose excess weight and keep it off.
Intermittent fasting (IF): Cycling between periods of regular eating and fasting (500 calories per day). The fast can be a full fast or just severe calorie restriction. The fast can last for hours, a full day, or longer.
Juice fast: An individual refrains from eating solid foods and subsists on fresh juices made from fruits and vegetables for a day to a week to several weeks. The idea is to detox from all the poor quality food you have been eating and cleanse your body as a re-boot.
Detox cleanse: Individuals consume raw vegetables, fruit, juices, and water. This can last for a period of days or weeks. One recent popular version involves drinking lemon juice, cayenne pepper, and maple syrup daily.
Daytime fast, then eating within a six to eight-hour wind: This is a version of the intermittent fast, involving periods during the day where you abstain from food, and then eating your meals during a very limited window of time.
Pros and cons of different fasts
In general, any kind of fast day likely means restricted physical activity. Individuals, especially seniors, may find fasting too taxing and young children, growing teens, or pregnant women shouldn’t fast. A one or two-day fast is unlikely to cause any long-term harm, and if it inspires you to then eat a healthy diet filled with wholesome food, then it’s probably safe. (Obviously, check with your doctor first.) You also can just commit to eating a healthier diet without fasting.
If you have certain health conditions or risk of diabetes, heart disease, breast cancer, and are seriously overweight or obese, then a doctor-guided fast may provide short- and long-term benefits. In an email, Andrea N. Giancoli, MPH, a registered dietitian and nutrition communications consultant, was not in favor of fasting diets if you've been diagnosed with diabetes or kidney disease.
Fasting diets could potentially trigger eating disorders in certain vulnerable individuals.
Ms. Giancoli cited possible side effects of fasting, like the risk of developing gallstones, hair loss, headaches, fatigue, volume depletion, electrolyte imbalances, muscle cramping, and constipation, although many of these can be managed with the guidance of a health professional.
Juice fasts are popular, but juices offer a concentrated source of sugars which dramatically elevate blood sugar levels, followed by a dramatic plummet, which can instigate lethargy and mood swings. Remember that when you juice, you’re drinking four to six fruits, which can equal more than 70-80 grams of sugar. It’s unlikely you would eat four to six pieces of fruit in one sitting, which is a standard “juice-fast” serving. There is no clear scientific evidence that a juice fast improves health.
Detox/cleanse diets that last for more than a day or two can instigate nutritional deficiencies, because they lack calcium, vitamin D, iron, and adequate levels of protein, and they can include expensive supplements. Don’t waste your money or put yourself in danger by buying supplements that promise to cleanse your system. Many of these supplements have undeclared ingredients or may be contaminated with drugs.
Fasting is not the only game in town
Remember that just making some small dietary changes can help to reduce the risk of ailments like heart disease. One study, accepted for publication in the British Journal of Nutrition in August 2016, suggests that swapping out a few processed high-fat foods for “healthy fat” foods can reduce total cholesterol, specifically LDL. So if you are looking for a diet change, and the idea of fasting seems like a poor fit, look no further than the Mediterranean Diet or DASH Diet, which have good science behind them. A commitment to these diets can improve your overall health and reduce the risk of many chronic conditions. You also will likely shed some weight if you decide to limit portions while following one of these dietary outlines. But, as mentioned, always consult with your doctor before starting any new diet.
Amy Hendel, also known as The HealthGal, is a Physician Assistant, nutritionist and fitness expert. As a health media personality, she's been reporting and blogging on lifestyle issues and health news for over 20 years. Author of The 4 Habits of Healthy Families, her website offers daily health reports, links to her blogs, and a library of lifestyle video segments.