My clinic often discusses intermittent fasting, a fashionable idea. I get it: limit your eating time but eat normally within it. No calorie counting. No dietary restrictions. Simple, adaptable. Intermittent fasting is popular for lasting weight loss in a busy lifestyle.
What is intermittent fasting?
Intermittent fasting (IF) is a placeholder for timing, a fundamental dietary lever. More correctly, intermittent fasting is an eating plan that extends your fasted state. Reduce the eating window. These previous articles discuss the most prominent time-restricted eating procedures (usually based on study designs):
How may time-restricted eating aid weight loss?
First, compare fed and fasted states, which encourage cellular development and breakdown and repair, respectively. Cell growth generates lean muscle mass and causes cancer, thus both can be good or bad. Many of our genes, especially those that regulate metabolism (how we digest and use dietary energy), are turned on and off daily by our circadian rhythms.
Early fasting occurs five to six hours after our last meal. After the sun sets, our metabolism slows and we sleep. In our current world of artificial lights, 24-hour convenience stores, and DoorDash, we are constantly hungry. We eat throughout the day instead of following our circadian rhythm.
Due to its effects on cellular processes and function, fasting has many health benefits, according to animal and human studies. When you fast, your metabolism changes from glucose to ketones, which activates many cellular signalling pathways to slow cellular development and boost repair and recycling. Repeated fasting increases insulin sensitivity, antioxidant defences, and mitochondrial activity.
Given that insulin resistance and inflammation cause many chronic disease, fasting may help lower diabetes, high cholesterol, hypertension, and obesity. Many short-term clinical trials show that intermittent fasting, specifically time-restricted meals, improves cardiometabolic health.
Is intermittent fasting effective for weight loss?
The data is ambiguous because to small sample sizes, brief intervention periods, heterogeneous study designs (sometimes without control groups), different fasting regimens, and participants of all shapes and sizes. Intermittent fasting and weight loss are mostly studied using time-restricted eating. A recent study reveals that reducing your eating window may help you lose weight.
New IF weight loss research
versus determine how time restriction affects weight reduction independently, we must compare a calorie-restricted diet with time restriction versus time restriction alone. A year-long study examined whether time-restricted eating with calorie restriction improves weight reduction and metabolic risk factors in obese patients more than daily calorie restriction alone.
The experiment included 18–75-year-olds with BMIs between 28 and 45, excluding those on weight-loss programs or taking weight-loss drugs. Participants were told to follow a 25% calorie-reduced diet (1,500 to 1,800 calories for males and 1,200 to 1,500 for women) with a specified protein, carb, and fat ratio. To ensure diet adherence (a common issue in diet research), participants were encouraged to weigh foods and required to keep a daily dietary log, picture their food, and record their meal times using a special mobile app.
Half of the individuals in the time-restricted eating group had to eat the prescribed calories within eight hours, whereas the other half in the daily-calorie-restriction group did not. All participants were advised to maintain their typical daily physical activity throughout the trial to exclude this variable and isolate food intake timing as the only difference between groups.
After a year, 118 individuals finished the research with similar diet adherence and composition. On average, the time-restricted eating group lost 18 pounds and the daily-calorie-restriction group lost 14 pounds. No significant difference in weight loss was found between the two groups or among subgroups by sex, baseline BMI, or insulin sensitivity. Similar improvements in blood pressure, lipids, glucose, and cardiometabolic risk variables were seen in both groups. This trial shows that reducing the eating window alone does not affect weight reduction.
What does the latest IF research mean to you?
A time-restricted eating approach appears to be a safe way to lose weight if you are not changing your diet.
A negative energy balance is the main reason time-restricted eating helps you lose weight. Restricting your eating time while maintaining your diet may reduce your daily calorie intake by a few hundred. If sustained, this lifestyle could lead to modest weight loss (3% to 8% on average, depending on existing data) and improvements in cardiometabolic markers like blood pressure, LDL cholesterol, triglycerides, and average blood sugar.
Lean muscle loss is IF's drawback.
Weight loss for cardiometabolic health is a good objective, but any intervention—including intermittent fasting—often causes lean muscle loss. Intermittent fasting protocols have shown this, which might be considered a negative effect. Resistance exercise and intermittent fasting are recommended because lean muscle mass boosts metabolism, regulates blood sugar, and keeps you fit.
Time-restricted eating (also known as intermittent fasting) may cause distinct cellular adaptations than totally fasted states, which may cause weight loss. It is unclear how much of the cardiometabolic benefits of fasting come from weight loss or cellular adaptations. It is likely a mix of both.
However, in a 24/7 society of 24/7 food possibilities, we may all benefit from aligning with our circadian biology and spending more time fasted and less fed each day.