The benefits of fasting: from the 5:2 diet to tricking the brain with low-calorie foods
- According to many nutritionists and dietitians, fasting is more healthy for us than people think
- We look at the different types of fasting and their various benefits
Fasting, the practice of abstaining from food, drink or both for a period of time, is a weight loss fad, but has been around for centuries.
Dr Bindya Gandhi, registered with the American Board of Family Medicine and the American Board of Integrative and Holistic Physicians, tried it herself while growing up in a traditional Indian household where she watched her mother and grandmother fast.
Gandhi notes there are different types of fasts in which people drink only water, or eat only fruit and nuts. She, like a growing number of people, is a fan of “intermittent fasting” – cycling between a period of fasting and non-fasting over a defined period of time.
Dale Pinnock, known as the Medicinal Chef, is a nutritionist, chef and author of Eat Your Way to Better Health. His intermittent fasting regime is called the 5:2.
For two days a week, you eat a limited diet, of just 500 to 600 calories, and for the other five days, you eat whatever you want. Says Pinnock: “Two days of self-discipline, followed by five days of glorious carefree living and the weight falls off you.”
Although his approach to fasting differs from Gandhi’s – she recommends patients start off with a 12-hour fast, then a 14-hour fast and eventually a 16-hour fast, eventually working to a 12-hour fast four days a week, a 16-hour fast two days a week, and a break one day a week, the theory behind fasting is the same. Gandhi says it boosts the immune system and resets blood sugar.
“Regular, intermittent fasting activates a gene called SIRT1. Often referred to as ‘the skinny gene’, it is involved in the repair and maintenance of cells to promote survival during times of dietary scarcity. Conveniently, SIRT1 also inhibits fat storage and is thought to deliver anti-ageing benefits,” says Pinnock.
Professor Valter Longo, founder of the Valter Longo Foundation, author of The Longevity Diet and named by Time Magazine as one of the 50 most influential people in health care this year, also advocates fasting, largely for overall health and longevity. But he does not advocate traditional fasting, which usually involves consuming nothing except water.
He uses the fasting mimicking diet, or FMD, as described in his book – a diet low in calories, sugar and protein and relatively high in fat. it uses natural ingredients and dieters follow it for a number of days every week.
Because of the types of food and low calories, the body does not recognise that it is being fed so it goes into fasting mode. Fasting in this way, Longo says, “gives the body an opportunity to eliminate damaged components and extra fat and replace it with newly generated components.” It also “reduces cholesterol, blood pressure, inflammation, triglycerides and abdominal fat”.
Longo led research at University of Southern California earlier this year which suggested that short, sharp regular fasts – two to four days each week over a six-month period – delivered huge health benefits. Additionally, participants’ immune systems appeared to be reinvigorated.
“Fasting in both mice and humans causes a temporary reduction in immune cells. In mice we know this is accompanied by stem-cell-based regeneration leading to new immune cells,” he said.
“What we noticed was that the white blood cell count goes down with prolonged fasting. Then, when you eat, the blood cells come back. When you starve, your system tries to save energy, and one of the things it can do to save energy is to recycle a lot of the immune cells that are not needed, especially those that may be damaged.”
Extended and regular fasting, he found, forces the body to use stores of glucose, fat and ketones, but also breaks down a significant portion of white blood cells. This triggers stem cell-based regeneration of new immune system cells. Prolonged fasting also lowers levels of IGF-1, a growth-factor hormone linked to ageing and cancer risk.
Fasting also seemed to reduce the body’s production of the enzyme protein kinase A – or PKA. When this happens, stems cells go into overdrive regenerative mode.
Longo and his team suggest a 72-hour fast can help protect against toxicity caused, for example, by chemotherapy as seems to be evidenced in a study conducted by the Department of Internal and Integrative Medicine at the Immanuel Krankenhaus Centre in Germany.
It confirmed the benefits of fasting for women with breast and ovarian cancer. Patients adhered to a fasting mimicking diet (with a 350-calorie daily allowance) and seemed to suffer less from the side effects of chemo, especially fatigue.
Researchers conclude that fasting could be an important addition to chemotherapy in the treatment of certain cancers, in alleviating side effects and because it may help chemotherapy drugs identify the cancer cells more efficiently. When fasting, cancer cells exhibit greater sensitivity to antitumour drugs than do normal cells. When their efficacy is enhanced, there is less need to increase the dose.
As Pinnock observes, though, fasting is difficult. “Either you’re starving and plagued with headaches and ‘hanger’, or you’re on the point of passing out and you’re permanently food fixated so there’s a temptation, as soon as you stop fasting, to binge.”
Hong Kong-based nutritionist Michelle Lau, who is founder of Nutrilicious, says fasting is not for her. “My body functions better with meals throughout the day. On top of that, I exercise regularly so I do need the energy (and nutrients) in my system as fuel for sports and to power me through the day at work.” She is also a healthy weight and says there are downsides to fasting, “extreme hunger, headaches, and a possible drop in blood sugar, all of which are symptoms I can’t afford to experience during my busy work days”.
She has clients, though, “who fast, feel great and shed weight by fasting regularly”.
Longo does not encourage fasting among people who are unwell, those suffering with eating disorders, the elderly or the frail.
Bindya adds lactating mothers and pregnant women to that list, along with those with chronic medical conditions. “Always talk to your doctor before starting a fast,” she says.
Longo’s tips for fasting for better health
• Think of a fast in terms of restricting feeding rather than abstaining – that way it’s less scary and you’ll approach it with positive eating habits.
• A ‘feeding window’ of 12 hours a day is optimal for health – so if your first meal begins at 9am, your last meal should be over by 9pm. Eating during time frame that is too short – four to six hours – can pose a risk for gallstone formation, especially among women. Limited feeding windows and/or alternate day fasting can also present problems, for examples in cardiovascular health. Too wide a window, though, and you could find other problems. If you eat for 15 hours a day or more, you could set up metabolic issues and sleep disorders. Don’t eat anything within three to four hours of bedtime.
• A pescatarian diet – seafood, but no meat – with low but sufficient protein, and a low sugar intake, is recommended.