Intermittent fasting is gaining popularity as a weight loss strategy and is thought to improve blood sugar control, blood pressure and cholesterol. Studies on rodents have shown that fasting between meals leads to slimmer healthier mice, regardless of what they ate. There have only been a few studies in humans and most have been short in duration with small sample sizes.
What is Intermittent fasting?
There are 2 main types of intermittent fasting. The 5:2 method allows you to eat normally for 5 days and then restricts calories to 500-600 calories for 2 days. The 16:8 method focuses more on when you eat. Typically encouraging eating for 8 hours, from 12pm to 8pm, and fasting for the other 16 hours.
Research shows that intermittent fasting the 5:2 method is effective for weight loss and improving cardiometabolic factors, but it isn’t more effective than daily calorie restriction of 25% fewer calories per day.
A recent study in JAMA Internal Medicine concluded that time-restricted eating (16:8 method) was ineffective for losing weight and did not improve cardiometabolic factors. The study found that 65% of the weight lost was lean mass not fat mass. This might be related to the fact that muscle growth and tissue repair is regulated by our circadian rhythm and the lack of protein in the morning with delayed eating may be the culprit. Our bodies metabolize food better early in the day rather than later at night. It might be more effective to restrict eating to 7am-3pm or 9am to 5pm and stop eating after that.
More research is required to determine if time restricted eating should start earlier in the day and include protein earlier. Longer term studies would also show if weight loss and cardiometabolic benefits achieved through the 5:2 method will last. Long term weight loss relies on the ability to stick with a plan long term and changing habits. Regardless of which plan you choose it should be one that you can live with long term and should always include healthy foods emphasizing fruits and vegetables, whole grains, legumes, and good fats.