Most of us are used to eating two to three meals a day often with snacks in between. For most cultures, this has become a standard eating pattern. In fact, some weight loss advice suggests eating more small meals throughout the day to support weight loss efforts.
However, the exact amount of meals you should eat per day for weight loss can vary. A 2010 study (1) analyzed the impact on weight loss between high and low meal frequency and concluded a high meal frequency with 3 meals and 3 snacks on a low calorie diet did not have any weight loss benefit compared to eating 3 meals a day.
What about eating one meal a day? Is this helpful, and sustainable, for weight loss? Instead of increasing meal frequency, some health experts and researchers are suggesting eating less during the day may have some positive benefits.
Whether it’s only eating one meal a day, only eating for specific times during the day or eating every other day, these eating patterns can all fall under the category of intermittent fasting (IF).
Intermittent Fasting has shown some positive health benefits and weight loss benefits, but it is still not a solution for everyone.
Why only one meal a day?
Eating only one meal a day is a type of IF that involves fasting all of the except for one meal. Most people pick dinner as their meal to eat, but it could be any meal.
This type of eating style doesn’t count calories or macronutrients. In general, food intake should consist of eating nutrient dense foods so you are getting antioxidants, vitamins and minerals.
The rest of the day you can drink calorie free beverages. If you are exercising, some plans also include a snack before and/or after exercise.
The thought behind this type of calorie restriction is to increase the amount of time your body is in a fasted state.
When you are in a fasted state, fat burn increases. The rationale for limiting your food intake to one meal instead of grazing throughout the day is to promote fat burn.
Proponents of IF suggest eating a higher meal frequency can lower fat burn because the body continuously uses energy from food eaten throughout the day.
By only eating one meal a day, even if it is a large meal, you are eating less food than if you were to eat all day.
Therefore, it is a method of calorie restriction not because you are focused on calorie counting, but simply because you are so limited in how much you can eat in one hour.
How to eat one meal a day
If you are starting to eat only one meal a day or other variations of IF, it will take an adjustment. You will feel hungry during the day when your body is used to eating.
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You can try to cut food intake back gradually to one meal a day instead of all at once. If you are exercising during the day, eating a protein and/or complex carbohydrate snack before or after exercise can be beneficial for maintaining muscle mass.
If you are exercising and considering IF, speak with your healthcare team for individualized guidance.
A general guideline is eating an hour a day so you are fasting the other 23 hours. Eating a meal, a day doesn’t mean you eat as much as you can for a few hours and leave feeling too stuffed to move.
You can eat whatever you want for eating one meal a day as calorie counting is not a factor. However, eating nutrient dense foods should still be a focus because you only have one opportunity to get all your nutrients in for the day.
What If you can’t eat just one meal per day?
If you don’t want to only eat one meal a day but want to try a similar method of calorie restriction, you could try other variations of IF.
Other variations of IF can include: fasting every other day, fasting 2 days a week and eating normally for the other 5, eating for a designated time frame every or most days.
Limiting your food intake to a specified time frame gives you more freedom that just eating one meal a day and may be more supportive if you exercise frequently.
Benefits of eating one meal per day
A 2017 study (2) concluded IF can enhance health and cellular resistance to disease even without weight loss.
This study looked at IF versus traditional calorie restriction in women over two years. The IF period was the month long fasting according to Ramadan which requires fasting during sunlight hours.
Interestingly, during the IF period, weight loss was lower compared to months of calorie restriction. However, IF had higher markers of urinary acetoacetate which suggests higher fat break down rates.
A 2017 study (3) looked at the short-term effects of IF in adults with type 2 diabetes. On average, participants followed IF for two weeks which involved fasting about 16 hours a day.
Participants had lower food intake during IF and lower postprandial blood glucose levels, but insulin resistance was not affected.
This short-term study suggests IF intervention for treatment with type 2 diabetes, but more research is needed.
There are an increasing amount of studies looking at the health and weight loss benefits of IF. There is need for more long-term trials for long term effects.
A 2015 review (4) on IF suggests studies with high level of clinical evidence are sparse. While some studies have shown various benefits for IF, more human research is needed before guidelines can be established for IF and health.
Conclusion: Eat only one meal per day may not be best for everyone
While IF is growing in interest and potential health benefits, it may not be the best fit for everyone. IF can have some unpleasant side effects such as: extreme hunger, fatigue, brain fog, weakness or increase tendency for binge eating or other disordered eating.
Fasting may not be recommended for various medical conditions or with certain medications. Therefore, you should consult your healthcare team before starting IF if you are on medication or have a medical condition.