Skipping lunch as part of intermittent fasting may help you lose weight. Potential negative effects of skipping meals include overeating later in the day and affecting your blood sugar levels.
Before skipping meals, research whether your health would permit intermittent fasting and what type of fasting schedule would work for you.
What Is Intermittent Fasting?
Intermittent fasting (IF) means that you only eat and consume calorie-containing beverages during certain hours of the day. One popular version is the 16:8 intermittent fasting diet, where you eat for eight hours of the day, then fast for the remaining 16 (and that fasting time includes the hours of the night you spend sleeping). During the fasting hours, you can drink noncalorie beverages, including water, unsweetened coffee and tea.
The hours of the day when you eat or fast are up to you. For example, some people who don't mind skipping breakfast might choose to eat between noon and 8 p.m., while others may want to eat from 9 a.m. to 5 p.m. Your ideal intermittent fasting time frame depends on factors like your work schedule, family mealtimes, what time of day you exercise and whether you prefer to eat breakfast in the morning or eat snacks later at night.
The 16:8 plan is popular, but there are endless combinations of intermittent fasting schedules. You could try eating during a 12-hour window and then fasting during a 12-hour window. Another option is the two-day fasting diet, where you eat normally for five days of the week and fast during the remaining two. On those fasting days you would limit your intake to about 600 calories per day for men and 500 calories per day for women.
In a review of literature published in the August 2017 issue of the Annual Review of Nutrition, researchers looked at how intermittent fasting affects metabolism in human subjects. They found that intermittent fasting can promote weight loss, and fasting was also associated with improved metabolic health biomarkers like decreased insulin and glucose levels.
"This overview suggests that intermittent fasting regimens may be a promising approach to losing weight and improving metabolic health for people who can safely tolerate intervals of not eating, or eating very little, for certain hours of the day, night, or days of the week," the study concluded. However, the review authors noted that much more research is needed on large groups of human subjects to provide more conclusive results.
Read more: How Eat-Stop-Eat Fasting Works
Skipping Lunch During Intermittent Fasting
Depending on your eating-fasting schedule, you may find that skipping lunch is part of your intermittent fasting routine. This is particularly true if you have a short "feeding" window and a longer "fasting" window — for example, a routine where you eat for six hours per day and fast for the remaining 18. You might eat from 3 p.m. to 9 p.m., bypassing traditional breakfast and lunch times altogether in favor of multiple small meals during your feeding window.
Before you commit to regularly skipping lunch or breakfast, educate yourself about the do's and don'ts of intermittent fasting. Compare the method to the typical weight-loss regimen of decreasing calories and ramping up exercise, and look realistically at your own daily routine and typical habits. While intermittent fasting works for some people, others experience consequences of skipping meals like decreased concentration and fatigue and find that intermittent fasting isn't sustainable for them in the long term.
Read more: 7 Strategies for Smarter Intermittent Fasting
Negative Effects of Skipping Meals
A study published in JAMA Internal Medicine in July 2017 suggested one major consequence of skipping meals: Failing to stick to your diet plan. The study assigned 100 metabolically healthy but overweight adults into one of three groups for a year.
One group followed a typical weight-loss diet by restricting their daily calorie intake, consuming 75 percent of their daily energy needs each day. The second group fasted on alternate days, consuming 25 percent of their daily energy needs on fast days and 125 percent of their daily energy needs on "feast" days. Finally, subjects in the control group continued eating as they had before.
Subjects were asked to lose weight for six months then maintain weight for six months. At the end of the study, researchers found that weight loss was similar for people in the calorie restriction group and people in the fasting group when compared with the control group.
However, they also noted that the dropout rate was highest in the fasting group — 13 out of 34 participants did not finish the trial, compared to 10 out of 35 in the calorie restriction group and 8 out of 26 in the control group.
The high dropout rate suggests that an intermittent fasting regimen can be difficult for some people to follow. Plus, because the fasting group and the calorie restriction group had similar outcomes, the research suggests that both options are valid methods for losing weight. So, if intermittent fasting is difficult for you to follow, you shouldn't be discouraged and give up on losing weight.
Intermittent Fasting Downsides
The consequences of skipping meals can be potentially harmful for people with diabetes, affecting blood sugar levels. According to the American Diabetes Association, eating regular meals can help manage your blood glucose levels if you have diabetes. "How often you eat is just as important as what and how much you eat," the association says.
Another negative effect of skipping meals is that, if you typically take a prescription medication with food, you may experience side effects from taking it on an empty stomach.
Before skipping meals, research potential downsides and speak to your doctor or a dietitian to ensure that intermittent fasting would be safe for you. If intermittent fasting is not advisable for you, chat with your doctor about adjusting your calorie intake or increasing your exercise routine to help you lose weight.
- Annual Review of Nutrition: "Metabolic Effects of Intermittent Fasting"
- JAMA Internal Medicine: "Effect of Alternate-Day Fasting on Weight Loss, Weight Maintenance and Cardioprotection Among Metabolically Healthy Obese Adults"
- University of Rochester Medical Center: "Overcoming Your Midafternoon Energy Slump"
- American Diabetes Association: "Dining on Time"