Among the multitude of fads and dietary recommendations, intermittent fasting may have faded into the background. However, a new study at Intermountain Healthcare Institute, Utah, shows that patients who had to have a cardiac catheterization done had a longer lifespan with intermittent fasting compared to those who didn't fast. Heart failure rates were also lower in the first group.
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The study will be presented on November 16, 2019, at the 2019 American Heart Association's scientific sessions. Researcher Benjamin Horne says, "We're finding that regularly fasting can lead to better health outcomes and longer lives."
Intermittent fasting is the practice of severely restricting food intake for some hours every day, or for certain days in a week. It is supposed to help curb appetite by slowing down the metabolic processes in the body. For instance, many popular weight-loss programs may recommend the 5:2 fast, where only 500-600 calories are allowed on two days a week, with normal eating patterns on the other five days.
Alternate fasting and feasting days is another pattern, with only 25% of the basic caloric requirement being allowed on fast days but the unlimited choice on the latter.
Most studies have looked at a small number of patients who fast to achieve weight loss. Many patients find this easier than daily calorie counting or food diaries. If, on the other hand, it is only an excuse to avoid all food discipline, it may be of no benefit.
The researchers recruited 2001 patients, who were having cardiac catheterization done at the healthcare facility, between 2013-2015. The participants underwent a survey of their lifestyle, including the practice of intermittent fasting. The same patients were followed up after 4.5 years.
The study also looked at factors like their age, sex, socioeconomic status, employment, education, and other demographic factors. Any risk factors for cardiac disease, any existing illnesses, any medications, and other treatments, and lifestyle factors such as alcohol and smoking, were all covered in the questions. Since these could all have a significant effect on long-term health and, therefore, survival, these factors were adjusted for when necessary.
The researchers had access to a relatively large population of intermittent fasters, because of the geographical area served by the facility. Much of the population here belongs to the Church of Jesus Christ of Latter-day Saints and marks the first Sunday of each month by fasting the whole of the day – skipping two consecutive meals and all beverages, typically until the evening meal.
The study showed that more patients survived, and heart failure rates were lower in the routine long-term intermittent fasting group than in the other group. This remained true even after adjusting for other risk factors.
The association is a strong one, but we can't tell if the fasting causes improved outcomes. However, the results do suggest a beneficial aspect of fasting in the health-related areas of life, indicating that more study is required.
Earlier studies by Horne showed that intermittent fasting done over the long term reduced the risk of diabetes and coronary heart disease. These studies, published in 2008 and 2012, are important in that they show how fasting can correct the metabolic abnormalities that develop over several decades to result in these serious health issues.
Mechanisms of benefit
Of course, most of the fasting in this diet was for a religious purpose, while in many diets that advocate fasting, it is for the purpose of accelerating weight loss. Horne says that the act of fasting confers health benefits through various biological pathways, irrespective of why people fast.
Most researchers think that the main effect of fasting is achieved via the reduction of abdominal fat, which in turn reduces the concentrations of leptin (a hormone that is linked to weight gain) while increasing adiponectin (a protein linked to inhibition of atherosclerosis and inflammation), and lowering LDL cholesterol levels
As to how intermittent fasting over the long term improves health, Horne suggests several routes may be involved. For instance, a fasting person shows changes in the hemoglobin level, the red cell count, the level of growth hormone in the blood, and the concentration of sodium and bicarbonate in the blood. Moreover, the body goes into ketosis, and autophagy is promoted, removing senile and defective cells.
Prior studies have shown that during fasting, the body uses up glucose, takes up glycogen from the liver, and starts to synthesize glucose in the liver. This is based on fatty acids, which serve as the starting point. In addition, fat cells release free fatty acids, which are then converted by the liver via a process called beta-oxidation, to provide a source of energy for all the body cells.
This change in the substrate used for fuel by the cells, called intermittent metabolic switching (IMS) or glucose-ketone (G-to-K) switchover, leads to a corresponding change in the cellular and molecular functioning of the brain cells, making them more efficient and tough.
All these improve health while particularly benefiting coronary heart disease and heart failure. Weight loss is also achieved by about 3% to 8%, depending on the duration. Inflammatory markers are also said to decrease.
When routine intermittent fasting is practiced over a long time, the body seems to be conditioned, ensuring a quick metabolic switch with shorter periods of fasting, rather than taking 12 hours as usual. As a result, the daily overnight fasting that is seen from the evening meal until breakfast the next day is enough to nudge the trigger for these beneficial processes – daily.
Sounding a warning
However, scientists caution that fasting may be potentially dangerous in some groups of people. For instance, they say, fasting should be avoided in pregnancy and when breastfeeding, by young children and by frail elderly people. (However, in Islamic cultures, the month-long religious fast is universally observed by all, young or old, man or woman, and by the vast majority of pregnant women, without obvious ill effects.).
Again, fasting is best avoided after an organ transplant, if the immune system is weakened, by people with acute or chronic infections, and by those who have bulimia, anorexia nervosa or another eating disorder.
What about people with chronic lifestyle illnesses like diabetes, high blood pressure, or heart disease and are on medications for these conditions? Well, say the researchers, fasting is possible with medical supervision to avoid the risk of severe hypoglycemia (a drop in blood sugar levels below normal) when these medications are taken without food.
Implications and future directions
The researchers want to go on to studies that answer this question of how intermittent fasting at even weekly intervals produces such significant benefits to health. They are also curious about how this brings about at least a partial resolution of chronic illnesses and boosts survival. The effects of fasting on the mind, on appetite, and the way the individual looks at hunger are additional research questions to be answered.
- Eurekalert.org. (2019). Intermittent fasting increases longevity in cardiac catheterization patients. https://www.eurekalert.org/emb_releases/2019-11/imc-ifi111219.php
- Intermittent fasting in cardiovascular disorders—an overview. Bartosz Malinowski, Klaudia Zalewska, Anna Węsierska, Maya M. Sokołowska, Maciej Socha, Grzegorz Liczner, Katarzyna Pawlak-Osińska, and Michał Wiciński. Nutrients. 2019 March; 11(3): 673. doi: 10.3390/nu11030673. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6471315/