Intermittent fasting comes in a few different ways: eating only at certain times of the day, not eating at all on certain days, or drastically reducing calorie intake on days of the week. The difference between intermittent fasting and dieting is that one is “intermittent” eating less, and the other is “continuous” skipping or eating less. And that’s what makes intermittent fasting so appealing to the general public: it doesn’t have to be starving all the time.
Calorie restriction is unnecessary if you limit your eating behavior to a certain time of day. So it makes sense that scientists routinely study intermittent fasting against calorie restriction. But now the question is, should intermittent fasting be more popular than calorie restriction? Can intermittent fasting help everyone achieve their health goals?
The comparison between intermittent fasting and calorie restriction is a debate about which is healthier, “better” or more successful in reaching your weight loss goals. But when it comes to these much-hyped eating habits, scientists and consumers view them differently.
Intermittent fasting “better” than calorie restriction may mean it’s not just about fat loss. And this comparison should also ensure that the two behaviors are not repeated.
What’s more, we don’t yet fully understand the long-term effects of intermittent fasting. Only animal studies have shown convincing evidence that various forms of intermittent fasting have significant health benefits in mice and rats, including increased lifespan.
But humans are different from these experimental animals after all. In studies involving humans, researchers often fail to precisely feed subjects, and subjects generally rely on recall to confirm what has been eaten, so the information is not always accurate. It can also be seen that when it comes to human trials of intermittent fasting, scientists also tend to get inconsistent results.
So where to find the answers to the above questions? We need to analyze carefully.
Calorie restriction is the act of reducing your daily calorie intake to below average levels while still getting the nutrients your body needs. Numerous studies have shown that calorie restriction can have health benefits: For example, in a long-term study called CALERIE published in The Lancet Diabetes and Endocrinology in 2019, scientists found that in normal and slightly overweight people In adults, 25 percent of calorie restriction resulted in decreased fat mass and improvements in overall cardiac and metabolic markers, including LDL cholesterol, blood pressure, insulin sensitivity, and more.
The key to intermittent fasting is when to eat, not what. Some popular intermittent fasting regimens include:
16:8 (16 hours without food, 8 hours with food);
5:2 (5 days of normal eating, 2 days of fasting or very few calories);
Fasting every other day or regularly, with occasional continuous fasts.
When we stop eating for a long time, the body undergoes a “metabolic switch”, that is, in a state of starvation, the body adjusts its basal metabolism from using glucose as energy to start breaking down muscle and fat.
This switch presents our body’s cells with a bioenergetic challenge of minor nutritional deficiencies, and this irritability appears to reduce inflammation, improve memory, and aid in diabetes management.
For example, a new study published May 25 in Nature Molecular Psychiatry found that compared with mice that followed a restrictive diet (10% calorie restriction) and ate as much as they liked, eating every other day Mice that ate food seemed to have better memory.
Mice that fasted every other day performed better on the maze test than mice that ate 10% fewer calories per day, and the only difference in their diet was timing (the intermittently fasted mice also ended up eating 10% fewer calories overall. % of calories). Intermittent fasting may have caused the mice to generate more newborn neurons, the researchers analyzed.
It should be noted, however, that so far, no long-term human studies have supported these conclusions.
Looking at this, it seems that intermittent fasting seems to be more effective than calorie restriction in reducing symptoms of Alzheimer’s disease or promoting other brain functions, although this is only an animal experiment. And general research shows that in obese people, both diets reduce body fat and improve blood pressure and cholesterol levels. This means that both intermittent fasting and calorie restriction may be good options, with intermittent fasting being more “successful” because it is easier for people to do.
In fact, however, in some populations, there is no real difference, and intermittent eating is even “less effective.”
A 2018 study published on JAMA Network compared intermittent fasting and calorie restriction for glycemic control in people with type 2 diabetes and found no observed advantage for the former. Intermittent fasting people eat 2 days of low calorie intake and 5 days of unrestricted regular eating, much like the popular “5:2” plan mentioned earlier, while calorie restrictors eat 1200-1500 calories per day .
Another study, published in JAMA Internal Medicine in 2018, looked at obese but healthy adults and found that alternate-day fasting had no advantage over calorie restriction in terms of weight loss or improved measures of heart health.
Meanwhile, a new study, published June 16 in Science Translational Medicine, looked specifically at whether intermittent fasting offers health benefits for “thin people” compared to daily calorie restriction . As a result, the team found that alternate-day fasting was less effective and that intermittent fasting was “nothing special.”
The trial was organised by a team at the Centre for Nutrition, Exercise and Metabolism (CNEM) at the University of Bath, UK, and participants were allocated to three groups.
Group 1: Fasting every other day, after the fasting day, eat 50% more than usual.
Group 2: Cut calories by 25% in all meals per day.
Group 3: Fast every other day (same method as group 1), but eat 100% more than usual one day after the fasting day.
The researchers observed that the calorie-restricted group (group 2) lost 1.9 kilograms in just three weeks, and the scans showed that the weight loss was entirely due to the loss of body fat. In contrast, group 1 experienced the same reduction in calorie intake and lost almost 1.6 kg by fasting alternate days and eating 50% more on non-fasting days, with half of this weight loss coming from fat decrease, and the rest of the decrease is muscle mass.
This suggests that in healthy adults, sustained daily calorie restriction leads to meaningful weight loss, while alternate-day fasting is less effective in reducing fat mass, and there is no evidence that fasting affects metabolic regulation or cardiovascular health have specific effects.
It also means that when you use intermittent fasting to reduce fat mass and improve health markers like blood pressure, cholesterol, and diabetes, science isn’t sure it’s superior.
Taken together, the evidence suggests that intermittent eating improves weight and/or metabolic health marginally compared with other diets in large studies of longer duration. Perhaps for most people, intermittent eating should be stopped.
