It is a fact that as a society, we overeat. For centuries humans struggled for food, and our forefathers kept switching between a state of “feast or famine.” Evolution has helped our bodies to respond to such alternate states very well. Modern-day science tells us that intermittent fasting helps us lose not only weight but also fight many otherwise incurable diseases.
But how does intermittent fasting work? Recent studies have clearly shown a strong correlation between the level of insulin that the body produces and weight loss. It is common knowledge now that lower insulin levels are beneficial for weight loss. Most of us relate insulin with diabetes. Every year a staggering 5 million people worldwide succumb to the disease. When we eat sugar or take excessive carbs, our blood sugar level rises. Insulin is the hormone that regulates blood glucose. Insulin extract glucose from the blood turns it into glycogen and stores in your liver or muscles as energy. Insulin also forces fat cells to absorb energy. In simple words, insulin makes fat, so more insulin made, more fat one stores.
Some use the analogy of lock and key for the action taken by insulin. It is the key that unlocks the cells to allow glucose, which in turn is used to consume the food we eat. Insulin resistance is when the key gets stuck or stops working efficiently. It results in constant cravings from the body cells for sugar while forcing the pancreas to produce more insulin until it gets fatigued and gives up. It is where diabetes sets in. But before reaching this stage, insulin resistance harms the delicate balance of removing glucose from the blood and consuming the food we eat. The outcome usually is rapid weight gain.
Apart from insulin, another hormone that is known as Leptin also plays a critical role. For a layman, Leptin is what gives us a feeling of satiety once we eat. But the role of Leptin for people suffering from obesity is the opposite. Similar to insulin resistance, Leptin resistance is another ailment that haunts during obesity and weight gain. In simple words, higher Leptin levels are supposed to give brain signals of satiety, but in Leptin resistant individuals, this signaling is whacked. The higher level of Leptin is present in the bloodstream, but the brain can’t acknowledge resulting in a person indulging in overeating.
The overall science behind both kinds of resistance is complicated and still not conclusive, but ample experimental results are indicating a strong relationship between eating habits and the resistance. Although there are many other factors, including genetics, age, gender, lifestyle during the early years, etc.
Then the question is how we can combat both kinds of resistance. Experiments on rodents indicate that the interval between famine and feast has a substantial impact on regulating the functioning of these hormones. In a 2005 study conducted on eight healthy males who were asked to fast every alternate day for 20 hours. They were allowed to eat for only four hours at a fixed time. After a couple of weeks, there was no substantial impact on weight or fat levels, yet the insulin sensitivity of all improved dramatically. The same amount of insulin now worked more efficiently. Doctors concluded that when we fast, the body breaks fat cells. These fat cells are the main culprit in distracting insulin to work properly. Once the fat cells break, it renders insulin the opportunity to work more efficiently.
In another study, the researchers from Yale experimented on rats by sending them from fed to fasting state and measured the rate of carbohydrate and fat metabolism. In fasting rats, Leptin levels decreased and activated a pathway that led to fat burning rather than carbohydrate burning. This phenomenon is behind ketogenic diets.
The rats’ use of stored glucose reduced, resulting in decreased sugar levels during fasting. Subsequently, levels of insulin and Leptin also reduced. The rats started breaking down body fat and turn it into ketones for energy. The team concluded that though, to start fat burning insulin levels needed to drop, a decrease in leptin levels was also essential for this to happen. Luckily, fasting stimulates both.
Another benefit of fasting is a reduction in the hormone IGF-1 or insulin-like growth factor 1. Cells in the body grow and reproduce as we take in energy. When we starve or fast, levels of IGF-1 which stimulate this process drops off. The reduced hormone acts as a signal to the body to go into repair mode and start fixing cell
An experiment that is widely quoted in this regard was performed at the University of Southern California’s Longevity Institute. In the research, mice were genetically engineered not to produce IGF-1. These mice surprisingly lived twice as long as mice with IGF-1. Also, these mice didn’t develop either diabetes or cancer.
In humans, people suffering from Laron syndrome never developed diabetes or cancer. The syndrome is a rare genetic mutation resulting in extremely low IGF-1 levels. Although we need increased levels of IGF-1 when we are young and growing, later in life, IGF-1 does more harm than good.
Intermittent fasting has shown consistent results in healthy individuals. One can pursue alternate day fasting or five-to-two days intermittent fasting for two to three months, with caloric intake limiting to 600 calories. The preferred fasting period is fifteen to sixteen hours a day. After such cycles apart from losing weight and shrinking one’s waistline, one should expect improvements in blood glucose level that prevents diabetes. Also, IGF-1 levels should plummet, thus decreasing the risk of cancer and age-related diseases.
How challenging is fasting? Unlike strict religious fasting, skipping meals for weight loss is flexible. Six hundred calories a day means one can enjoy breakfast and a light dinner. Furthermore, one doesn’t need to do it on consecutive days. Choose a schedule and try to stick to it. On regular days, we sometimes eat even when our bodies do not need food. Our brain sends false signals as we are used to eating at a particular time, or we smell something appetizing. However, hunger pangs can be alleviated by drinking coffee or tea (of course without sugar and milk) or keeping oneself busy.
Informative. Intermittent fasting is usually associated with keto dieting. Why is that?