Intermittent fasting has fans in Jennifer Aniston, Chris Hemsworth – and it may lower type 2 diabetes risk; experts say when and what you eat matter, too

Fasting aids in weight loss, can reduce inflammation to fight arthritis, safeguards the heart, boosts brain function, protects against cancer and improves sleep
Fasting also reduces insulin resistance and blood glucose levels to lower diabetes risk; eat a whole food, plant-based diet and eat early for best results

Wellness

Sasha Gonzales

Published: 6:15pm, 12 Nov 2023

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Jennifer Aniston, Halle Berry, Scarlett Johansson, Hugh Jackman and Chris Hemsworth have more than celebrity in common. These Hollywood stars have also tried, or follow, intermittent fasting – to stay in shape and improve their overall health.

Called IF for short, intermittent fasting is a dietary approach that alternates between periods of feeding and fasting.

IF practitioners restrict their eating window to a certain number of hours a day or certain days of the week, voluntarily fasting the rest of the time.

During the fasting period, the body does not have enough glucose for energy, so it breaks down stored fat instead, a process known as ketosis.

Intermittent fasting may lower the risk of type 2 diabetes by reducing insulin resistance and blood glucose levels. Photo: Shutterstock

The benefits of IF are well documented. In addition to weight loss, it is found to:

reduce inflammation and improve conditions associated with inflammation, such as arthritis;
protect the heart;
boost brain function;
protect against cancer;
relieve digestive issues;
improve sleep;
increase life expectancy; and
lower the risk of type 2 diabetes by reducing insulin resistance and blood glucose levels.

But it seems that when you eat matters, too, especially in relation to the risk markers for type 2 diabetes. A recent Australian study found that a fasting diet which focuses on eating early in the day could be the key to reducing the risk of developing the disease.

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For the study, which involved more than 200 participants and spanned 18 months, researchers from the University of Adelaide and South Australian Health and Medical Research Institute compared two different diets, a time-restricted, intermittent fasting diet and a reduced-calorie diet, to see which one was more beneficial for people who were prone to developing type 2 diabetes.

The study was published in the scientific journal Nature Medicine.

While participants on both diets experienced similar amounts of weight loss, those who fasted for three days during the week, only eating between 8am and 12pm on those days, showed a greater tolerance to glucose after six months than those on a daily, low-calorie diet, according to senior author, Professor Leonie Heilbronn from the University of Adelaide.

Professor Leonie Heilbronn is from the University of Adelaide. Photo: University of Adelaide

“Participants who followed the intermittent fasting diet were more sensitive to insulin and also experienced a greater reduction in blood lipids than those on the low-calorie diet,” she added.

Type 2 diabetes occurs when cells in the body’s muscles, fat and liver become resistant to insulin, resulting in insufficient uptake of glucose from the bloodstream and an increase in blood glucose levels, says dietitian Dr Mia Holm, manager of the Lifestyle Management Centre at Hong Kong Adventist Hospital.

There is a hereditary component to type 2 diabetes, but family history is just one of several risk factors for the disease. Inactivity, being overweight or obese, and having excess body fat, particularly around the abdominal area, are also factors that make someone more prone to developing type 2 diabetes, Holm says.

Plant-based foods are more satisfying than refined and processed ones, says dietitian Dr Mia Holm, manager of the Lifestyle Management Centre at Hong Kong Adventist Hospital. Photo: Mia Holm

While the differences between the two Australian study groups were lost after 18 months, the study sheds light on the benefits of a new dietary interventional approach, says Professor Alice Kong from the department of medicine and therapeutics at Chinese University of Hong Kong.

“It’s too early to say that this approach is much better than the traditional approach of calorie restriction (with regard to glucose tolerance). As you can see, the effects were gone at 18 months, and the long-term effects of IF and time-restricted diets have not been proven.

“It’s not just when or how often we eat, but also what and how much, and being consistent with these habits, that can help us maintain a healthy lifestyle and minimise our risk of developing type 2 diabetes.”

It is not just when or how often we eat, but also what and how much, says Professor Alice Kong at Chinese University of Hong Kong.

If you want to try IF, Holm says it is easier to start with a 12:12 fasting-eating pattern – fasting for 12 hours and eating for 12 hours. Once you are comfortable with this schedule, you may gradually increase it to 14:10 and then 16:8.

“According to various studies, skipping dinner is better than skipping breakfast, since eating breakfast supports a healthy circadian rhythm,” she adds.

“For those looking to align with their circadian rhythms, eating between 8am and 6pm might be the ideal schedule. If skipping dinner is not possible, I recommend consuming the majority of your calories during the day, having a lighter dinner and eating at least three to four hours before bedtime.”

Both the American and Canadian Diabetic Associations for managing type 2 diabetes advocate having a whole food, plant-based diet. Photo: Shutterstock

She warns that IF is not suitable for children, teenagers, pregnant or breastfeeding women, and individuals who are physically fragile or have nutritional deficiencies.

IF is not a licence to consume unhealthy foods, such as sugar- and fat-laden cakes and pastries, soft drinks, deep-fried products that are high in saturated fat and salt, and ultra-processed or junk foods that offer zero nutrients. To reap the health benefits of IF, you should make wholesome food choices.

“If you consume unhealthy food during the feeding period, you are essentially putting poor-quality fuel into your body, and this can lead to increased inflammation, oxidative stress and an imbalance in your gut microbiome,” says Holm.

Carbohydrate-rich foods such as instant noodles may cause blood sugar levels to rise quickly, increasing the risk of developing type 2 diabetes. Photo: Shutterstock

Studies have shown that people who consume high amounts of saturated fat – commonly found in meat – and animal fats have twice the risk of developing diabetes compared to those who consume lower amounts, Holm notes.

Kong adds that the overconsumption of foods with a high glycaemic index – carbohydrate-rich foods that cause our blood sugar levels to rise quickly, such as white bread, instant noodles and some breakfast cereals – and sugary beverages also increases our risk of diabetes.

For managing type 2 diabetes both the American Diabetic Association and its Canadian counterpart advocate having a whole food, plant-based diet, Holm says. Made up of whole grains (such as brown rice and oats), green leafy vegetables, fruit, legumes, beans, seeds and nuts, this diet is rich in fibre and low in unhealthy fats, salt and sugar.

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Holm says that hunger pangs should subside after 30 minutes if you feel hungry during the fasting period. Drinking zero-calorie fluids such as water or plain tea can help quell your hunger.

She adds that this is why it is crucial to eat adequately and nutritiously during the feeding period, particularly if you are physically active. Because they are high in fibre and nutrients, plant-based foods will satisfy you more than refined and processed ones.

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