Intermittent fasting has been trendy lately, as celebrities like Jennifer Aniston embrace it. Trends come and go, but intermittent fasting may have staying power, thanks to new research supporting its benefits for weight loss and metabolic health. Research into calorie restriction eating is still in its early stages but that hasn’t stopped people from jumping on the fasting bandwagon.
You might wonder what this eating approach is exactly. Intermittent fasting is not a diet, but a pattern of eating. It describes eating plans that cycle between periods of eating and fasting. All these approaches have one thing in common: they restrict the amount of time you spend eating and increase the time you spend fasting or without food.
The more conventional approach to losing weight is to restrict calories and reduce the total calorie content of your diet, but that’s not always easy to do. You feel deprived when you cut back on calories too much and your body can rebel. Plus, cutting back on calories can slow your resting metabolism and, paradoxically, make it harder to lose weight.
Intermittent Fasting and Weight Loss
So, how does intermittent fasting compare to calorie restriction for losing bodyweight? An analysis of 25 studies published in the Annual Review of Nutrition looked at intermittent fasting head-to-head with calorie restriction. With intermittent fasting, you eat within defined time intervals and fast outside those times.
One of the most popular approaches to intermittent fasting is time-restricted eating, a form of intermittent fasting. You can structure time-restricted feeding in different ways but the most popular is a 16:8 structure. You eat during an 8-hour window period and fast for 16 hours.
The reason the 16:8 structure is so popular is that you sleep during some fasting time. Most people structure this type of fast by eating an early dinner, and then eating a late breakfast or early lunch the next day.
Other approaches to intermittent fasting include:
The 5:2 structure: 5 days of eating and 2 days of fasting each week
Alternate day: Fasting one full day and eating the next.
The latter two approaches are more challenging since you go an entire day without eating. Most people start with the 16:8 structure since it’s so user-friendly.
Intermittent Fasting Has Weight Loss Benefits
In the study, intermittent fasting led to similar weight loss as a calorie restriction of 500 calories per day. Intermittent fasting offered additional perks too. In the study, it lowered LDL cholesterol (a risk factor for cardiovascular disease), blood triglycerides, and blood pressure. Plus, it improved insulin sensitivity. These improvements all bode well for heart health.
The study also found that people who fasted intermittently add fewer calories, around 20% less, without consciously restricting calories. Intermittent fasting focuses on the timing of food intake, rather than calories or the content of the diet.
Did the fasting structure affect weight loss in the study? Participants lost more weight on the 5:2 intermittent fasting structure and the alternate-day fasting than on the 16:8 structure. Eating within a certain window period doesn’t seem to be as effective, at least not in this study as full days of fasting. Still, all forms of intermittent fasting, including time-restricted eating, led to weight loss.
The benefits of time-restricted feeding and the 16:8 intermittent fasting structure is it’s easier to stick with since you’re not fasting for a full day at a time. Even if it didn’t lead to as much weight loss in the study as full-day fasting, it’s an excellent starting point for those new to fasting. The fact that it’s easier means you’re more likely to do it consistently.
Will going without food that long make you ravenously hungry? Most research shows that time-restricted feeding doesn’t lead to an increase in appetite. In fact, some studies show that time-restricted eating reduces appetite and the desire to eat.
Is Intermittent Fasting or Time-Restricted Eating Right for You?
As with most eating plans, intermittent fasting isn’t for everyone. If you have medical problems, take certain medications, or are pregnant or breastfeeding, this type of dietary approach may not be for you. It must be comfortable enough for you to do it, and it must fit into your lifestyle.
When you first begin an intermittent fasting program, you may experience hunger or headaches until your body adapts. But over time, your body adjusts, and the side effects usually subside. Although intermittent fasting doesn’t specify what to eat, you’ll get the most benefits if you choose nutrient-dense foods and drink enough fluids to stay well-hydrated. Make the foods you eat count in terms of nutrition. The most important thing you can do, whether you’re trying to lose weight or not, is to provide your body with proper nutritional support.
The Bottom Line
Intermittent fasting is a different approach to weight loss, and it seems as effective as cutting calories. If you start, begin slowly by trying the 16:8 plan. It’s the most beginner-friendly. If you haven’t tried intermittent fasting yet, try it now! You can even start by going 12 hours without food overnight (the easiest way). Then, gradually build up to 16 hours of fasting. But most people don’t find 16 hours of fasting to be difficult. If you structure it properly, it only involves skipping breakfast. But everyone’s a little different. See how it works for you!
References:
- Welton S, Minty R, O’Driscoll T, Willms H, Poirier D, Madden S, Kelly L. Intermittent fasting and weight loss: Systematic review. Can Fam Physician. 2020 Feb;66(2):117-125. PMID: 32060194; PMCID: PMC7021351.
- Annual Review of Nutrition. Vol. 41:333-361 (Volume publication date October 2021) doi.org/10.1146/annurev-nutr-052020-041327.
- “Diet Review: Intermittent Fasting for Weight Loss | The ….” hsph.harvard.edu/nutritionsource/healthy-weight/diet-reviews/intermittent-fasting/.
- “Research on intermittent fasting shows health benefits ….” 27 Feb. 2020, nia.nih.gov/news/research-intermittent-fasting-shows-health-benefits.
- Ravussin E, Beyl RA, Poggiogalle E, Hsia DS, Peterson CM. Early Time-Restricted Feeding Reduces Appetite and Increases Fat Oxidation But Does Not Affect Energy Expenditure in Humans. Obesity (Silver Spring). 2019 Aug;27(8):1244-1254. doi: 10.1002/oby.22518. PMID: 31339000; PMCID: PMC6658129.
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