It’s probably not a surprise that late-night refrigerator raids aren’t great for your waistline—but a new study has shed light on why eating when the rest of the region is asleep leads to weight gain. According to researchers at Brigham and Women’s Hospital, people who eat late have more intense appetites than those who close the kitchen doors after sundown, because eating late at night has a profound impact on the appetite-regulating hormones ghrelin and leptin. Additionally, the study, which was published in Cell Metabolism, found that night owls who prowl the pantry after dark burn fewer calories than early birds.

“We found that eating four hours later makes a significant difference for our hunger levels, the way we burn calories after we eat, and the way we store fat,” author Nina Vujovic, PhD, a researcher in Brigham’s Division of Sleep and Circadian Disorders, said in a Science Daily report.

What does eating late at night do to you?

According to the Brigham study, shifting your meals to later in the day (by skipping breakfast, for example, and eating a late dinner) slows metabolism—making you burn fewer calories—and stimulates hunger and hunger hormones that lead to food cravings, especially for salty and starchy foods.

The research was based on a controlled clinical trial with 16 overweight and obese participants. Except for meal timing, everything that could be controlled was identical: exact foods and portions, calorie content, amount of light time, amount of dark time, physical activity and posture.

The study measured reactions to a more traditional eating pattern, with breakfast at 8 AM, lunch at noon, and dinner at 5:30 PM. It also tested a late eating pattern: no breakfast, lunch at noon, dinner at 5:30 PM, and a late-night supper at 9:30 PM.

The results verified what many late-night snackers have experienced: late eating doubled the likelihood of feeling hungry and significantly increased how much a person wanted to eat. It also led to increased desire to eat starchy foods, meat, salty foods and dairy—which might be why a fast-food burger, fries and milkshake seem to hit the spot after a night out.

The long-term effects of night eating

Night eating is a concern because research has found meal timing interacts with our circadian rhythm—and that all-important sleep-wake cycle—and impacts health. The Brigham study and others have found late night eating actually alters the body’s circadian rhythm, or the day/night and light/dark patterns.

And we know that abnormal circadian rhythms and chronic sleep problems are associated with poor health and metabolic disorders. For example, night shift workers have been shown to have a high risk of obesity, type 2 diabetes, and cardiovascular disease.

The effects aren’t only seen in adults, however. Research has shown late eating also can affect the health of school-aged children, and the timing of the dinner meal is a factor in obesity. School-age children in Spain who ate dinner late rather than early had double the chances of being overweight or obese. Not only did these young late eaters have a higher waist-circumference, but they also had higher inflammatory markers and more circadian-related disturbances than early eaters.

Why does late night eating cause weight gain?

While science doesn’t state with certainty that later meal times cause obesity or weight gain, it clearly shows a link between them. And we know that after-hours munching does increase the risk of weight gain. As the Brigham study shows, it stimulates hunger and appetite (thanks to its effects on the balance of the hunger hormones leptin and ghrelin) so you’ll want to eat more calories. And to make matters worse, the study also suggested that late night eating may slow fat burning and increase fat storage, a phenomenon adding credibility to the expression, “Eating late equals weight.”

Why does my appetite increase at night?

There are plenty of reasons why your hunger could increase at night, and those reasons are likely different for every person (unless the air is filled with the scents of good cooking nearby—which would make your tummy rumblings easier to explain).

Here are some of the more common reasons why you may feel hungry after bedtime.

• Skipping breakfast:

  You wouldn’t be the only one guilty of skipping breakfast (yes, the most important meal of the day!) and then “grabbing a bite” for lunch. As the Brigham study shows, eating earlier in the day helps control your appetite hormones. You may not be eating enough earlier, so you feel hungry—and eat more—later. This finding underscores the importance of a balanced breakfast, and a healthy mid-day meal, in avoiding binge eating.

• Stress eating:

  Many people “run on fumes” during the day. They are go-go-go, focused on their job, family or other responsibilities and paying little attention to their own needs—especially the need for smart and healthy nutritional choices. This anxiety could lead to unhealthy or insufficient food choices during the day, night-time binge eating, or another eating disorder.

• Emotional eating:

  An eating habit that uses food for mental health, this “crying into a pint of ice cream” meal is the opposite of mindful eating. Emotional eating tends to happen at the end of the day, maybe once the laptop is closed for the night, or the kids are in bed, and it feels OK to take some time for yourself. Often, this translates into night eating.

• Alcohol:

  If you drink alcohol, this lowers inhibitions, which could make it easier to give in to night-time meal cravings.

Should I still eat if I feel hungry at night? Identifying hunger cues

As the science shows, you should try to avoid eating at night. Late-night snacking affects your metabolism, adds calories you likely don’t need to your diet, and can make you hungry and affect your meal choices the next day, increasing your risk of obesity. If the hunger is from boredom or drinking alcohol, try distracting yourself. The hunger may pass, giving you the chance to wake up with an empty stomach and hungry for breakfast, which will help you start a proper circadian rhythm eating pattern.

If you are truly hungry, your appetite won’t go away so easily, so you might have to eat. In that case, try eating an apple or other unprocessed food without added salt or sugar—two substances that can make it hard to stop eating once you’ve started.

How to curb your appetite: 3 techniques

1. Mindful eating:

   Also called intuitive eating, this technique teaches you to recognize to your body’s hunger cues (as opposed to thirst, emotion or stress). It focuses on healthy eating habits, movement and satiety (that feeling of fullness) over appetite suppressants or focusing on weight loss.

2. Physical activity:

   Regular exercise is a perfect fit for almost every healthy eating plan because it can help control your appetite by influencing the hormones that stimulate feelings of hunger.

3. Get good sleep:

   Sleep patterns can influence your levels of the hormone ghrelin, so practicing good sleep habits is important. Getting healthy sleep not only helps you feel not-so-hungry, but it boosts your health in other areas as well.

” I just don’t have time to work out,”

Thankfully, there’s a solution: high-intensity training.

What are high-intensity workouts?

When we’re talking about high-intensity interval training, it refers to performing short bursts of exercises followed by short rest periods. You alternate between the two (work periods and rest) for the duration of your workout.

A great example of a HIIT workout is the standard tabata. In a tabata, you do 20 seconds of intense exercise followed by 10 seconds of rest. You repeat this eight times, for a four-minute workout. While some people stop here, others choose to extend it further. To make your workout even spicier, you can do this for four rounds, with one minute of rest in between each. This gives you a 20-minute workout—be prepared for your lungs to burn!

To be clear, just about anything can be turned into a HIIT workout—it’s not just tabatas. Ten seconds of sprinting followed by 45 seconds of rest is HIIT. So is 15 seconds of all-out peddling on a stationary bike followed by 30 seconds of rest. HIIT workouts often use only the weight of your body. However, they’re incredibly versatile. And if you want to increase intensity even more, throw in some dumbbells! Yes, even traditional weight training can have an aerobic twist and become more high-intensity.

Because high-intensity workouts demand that you give your max effort, they’re typically shorter in duration—usually somewhere between 10 and 30 minutes. Make no mistake, though. These will get your heart rate up.

Are high-intensity workouts good for you? Health benefits

Why should you consider adding HIIT workouts to your weekly fitness schedule? Here are just a few health benefits.

1. HIIT workouts can promote fat loss

HIIT isn’t like other types of cardio. Research suggests that HIIT can trigger fat loss. In one clinical study with 44 female university students, four weeks of HIIT significantly decreased their BMI, body fat percentage, and total body fat mass. It also increased their muscle mass.

2. You can add muscle to your frame

HIIT isn’t only aerobic. If you haven’t been that active and want to get stronger, high-intensity exercise is your friend. One study using hockey players showed that HIIT triggered positive effects in the thickness and power of their muscles. The study mentioned above with female university students also showed a marked increase in muscle mass over the four weeks.

How does this happen? Well, research tells us that HIIT can stimulate the cellular responses that encourage muscle mass, along with increasing the expression of proteins involved in muscle growth.

3. High-intensity interval training can promote already-healthy blood pressure

One study showed that HIIT is better at maintaining already-healthy blood pressure compared to more moderate-intensity exercise. Another study came to a similar conclusion, noting that people who did HIIT compared to endurance training (meaning the HIIT group exercised less) were able to similarly support blood pressure already in normal range. In other words, they did less work for similar benefits. Another 2022 meta-analysis of 10 articles using 266 participants who were 60 years of age or older showed that those who participated in more than four weeks of HIIT were better able to promote already-healthy blood pressure compared with the control group.

Even low-volume HIIT (meaning less than 15 minutes of high-intensity exercise) can support already-healthy blood pressure and healthy glucose metabolism.

Get your heart rate up, challenge your lungs, and support your health.

4. HIIT can encourage already-healthy blood sugar levels

Research suggests that HIIT supports healthy insulin sensitivity better than continuous exercise. And a 2022 meta-analysis examining 19 clinical studies found that there was significant support for already-healthy fasting glucose, HbA1C and insulin levels in groups that did HIIT versus the control group.

In other words, HIIT can, support already-healthy blood sugar levels.

5. HIIT is good for the brain

It’s not just about the physical benefits. Exercise can improve your memory and cognitive ability.  High-intensity exercise specifically can improve how fast you process information.

And, it’s great for your mental health! One systematic review from 2022 showed that HIIT can improve your mood and mental well-being, while fighting perceived stress.

How does high-intensity training (HIIT) work?

High-intensity interval training works by putting you through periods of high-intensity exercise followed by low-intensity rest periods. You perform this for rounds and end up with a shorter workout that’s miraculously more effective than many longer programs.

Types of high-intensity workouts

As you can now tell, there are infinite ways to tackle your HIIT training. When coming up with your programming, note that there are four training variables you want to address.

• Intensity

  : Intensity refers to a few variables, including how fast you move, how much weight you lift (if applicable), and for how many reps, in a single workout.

• Duration

  : This refers to how long your HIIT workouts last. As we mentioned, they typically range from approximately 10 to 30 minutes.

• Frequency

  : How often do you perform your HIIT workouts in a week? That’s frequency!

• Exercise recovery

  : Exercise is nothing without recovery. Your HIIT workouts are when you stress your body and break it down (in a good way). Recovery is when it builds back up to be stronger than before. We call that a win!

How often should you do high-intensity workouts?

There’s no magic number when it comes to HIIT workouts. What matters most is that you give your body enough rest in between workouts.

Some high-intensity workouts won’t be quite as demanding as others. So, a day of rest might be enough. However, other workouts might have you sore for a few days. Listen to your body and rest accordingly

As a general rule, many people opt to do high-intensity training two or three times a week and often incorporate other training methods in between, for variety (like strength training or endurance cardio/steady-state cardio). Even if these other training modalities don’t get your heart rate up, there offer many other health benefits—resistance training, in particular.

Variety is the spice of life. Mix up high-intensity, moderate-intensity, and low-intensity training for optimal results.

Could high-intensity training be dangerous? Health tips

Just about any type of training can be dangerous if you go about it the wrong way. The same goes for HIIT-style workouts.

If you’re being monitored for any health condition—especially involving your heart—speak with your doctor first. You should also speak with your provider first if you haven’t been active for a long period of time.

However, also note that one systematic review of 23 studies with 1,117 participants found that HIIT has a low rate of major adverse events. Another clinical study with 29 participants showed that HIIT was safe, effective, and enjoyable. It even supported already-healthy blood pressure and mood improved.

Don’t forget warm-ups, cool-downs, and ample recovery periods between workouts.