Is Eating Late at Night Bad for Weight Loss?

Tapering down your calorie intake over the course of the day — eating breakfast like a king, lunch like a prince and dinner like a pauper — is thought by many to lead to a faster rate of weight loss.

The idea is that calories eaten in the evening are more likely to be stored as fat compared to eating those very same calories earlier in the day.

However, you’ll also find people who recommend the opposite, claiming that a large dinner will help rather than hurt your body composition.

So who’s right? Do calories become more fattening if you eat them later in the day? Or is eating your largest meal at night the way forward?

Late Night Eating and Weight Loss

The idea that eating a meal late at night puts the brakes on weight loss appears to come from a couple of studies published in the 1970’s.

They show that subjects lost weight when a single daily meal was eaten in the morning. When the same meal was eaten in the evening, weight was lost more slowly. In some cases, subjects actually gained weight.

Unfortunately, these studies didn’t last very long (1-3 weeks). And information about how the research was done is very hard to come by.

Crucially, we don’t know if the subjects were closely supervised in a metabolic ward, or if they were simply given instructions on what to eat and then left to their own devices.

The potential for unreported dietary deviations skewing the results is far greater with the latter than it is with the former.

There is also observational research reporting a link between the number of calories consumed in the evening and a higher BMI [2].

However, observational studies tell you nothing about cause and effect. They might show a link between eating late at night and weight gain, but they don’t show that one is causing the other.

A number of controlled trials have looked at how the distribution of calories throughout the day affects your body composition.

The ones we’ll be looking at are those that are the best designed, or are cited most frequently to prove or disprove the effectiveness of one particular dietary approach versus another.

Greater Weight Loss With High-Carb Dinner

First up, we have a study showing that eating a larger carbohydrate-rich meal later in the day helps rather than hinders weight loss.

Here’s how it was set up.

A group of 78 obese police officers was assigned to one of two groups [6]. Both groups were prescribed the same diet. The only difference was in the way carbohydrate intake was distributed throughout the day.

• In group A, most of the carbohydrate for the day was eaten at dinner.
• In group B, carbohydrate was spread evenly throughout the day.

Interestingly, the carbohydrate-for-dinner group lost an average of 25.5 pounds (11.6 kg). Subjects in the control group, who spread their carbohydrate intake over the course of the day, lost 20 pounds (9.1 kg).

The carbohydrate-for-dinner group also experienced much less hunger than the control group.

The researchers think that this dietary pattern affects both leptin and ghrelin levels the following day, enhancing satiety, reducing hunger and making it easier to stick to the diet [7].

The carbohydrate-for-dinner group also saw better improvements in markers of inflammation, insulin sensitivity and blood sugar control.

This study does show a clear benefit to eating more carbohydrate at night. But the difference was still relatively small, amounting to 5.5 pounds (2.5kg) over a six-month period, or less than 1.1 pounds (0.5kg) per month.

What’s more, the prescribed diet was relatively low in protein. Had both groups eaten more protein, which itself can help with hunger control, the difference in weight loss between the two groups may have been even smaller.

In addition, nobody in the study was following any kind of structured training program. So we don’t know how exercise would have affected the results.

Big Breakfast Boosts Weight Loss

Two years later, a follow-up study appeared, this time with a completely different set of results.

That is, a big breakfast and small dinner led to a faster rate of weight loss than a small breakfast and large dinner.

For the study, researchers assigned a set of overweight and obese subjects to one of two groups [8].

The first group ate progressively smaller meals over the course of the day. Breakfast contained 700 calories, lunch 500 calories and dinner just 200 calories.

The second group did the exact opposite. They ate a small breakfast (200 calories) and a large dinner (700 calories).

After 12 weeks, here’s what happened:

• The big breakfast group lost, on average, 19 pounds (8.7kg).
• The small breakfast group lost just 8 pounds (3.6kg).

Both groups lost weight for the first couple of months. But the small breakfast/large dinner group fell off the wagon at week 8, where they started to regain some of the lost weight.

This isn’t surprising, given the large difference between the two groups in terms of hunger (the physical need for food) and satiety (the sensation of feeling full after eating).

Average daily satiety scores were around 30% higher in the small dinner/large breakfast group compared to the large dinner/small breakfast group.

Differences in weight loss between the two groups may have had more to do with the large protein-rich breakfast (which contained around 55 grams of protein) suppressing hunger during the day than it did with a large dinner somehow slowing weight loss.

In addition, subjects were prescribed just three meals a day. The meal plans given to the police officers in the earlier trial included a mid-morning and mid-afternoon snack. This may have blunted their hunger, making it easier to get through the day without deviating from the diet.

What’s more, this wasn’t a study where the subjects were living in tightly controlled conditions. They were given some diet plans, and met with a dietitian every two weeks. Other than that, they were on their own.

What happens when compliance is taken out of the picture?

In other words, how does meal timing affect body composition when subjects are confined to a metabolic ward, where food intake is supervised a lot more closely?

That’s what a research group from the U.S. Department of Agriculture wanted to find out [10]. They took a group of 10 women, aged 23-39, and assigned them to one of two groups. Both groups were given a diet providing an average of 1,911 calories daily.

For six weeks, the first group ate most (70%) of their calories early in the day. Group two consumed the majority (70%) of their calories later in the day. For the second six weeks of the study, the groups switched to the alternate meal pattern.

As I mentioned earlier, this was a metabolic ward study. Rather than being given some meal plans and told to go away and get on with it, the women taking part in this study lived in a metabolic suite 24 hours a day, 7 days a week. This gave the researchers a lot more control over what their subjects ate.

During both periods, subjects received four meals daily. Breakfast was served between 8.00am and 8.30am, lunch between 11.30am and 12.00pm, while dinner was eaten between 4.30pm and 5.00pm. An evening snack was served between 8.00pm and 8.30pm.

During the PM meal pattern, when calorie intake was greatest in the afternoon and evening, the women consumed 15% of their calorie intake at breakfast, 15% at lunch, 35% at dinner, and 35% at the evening snack. This pattern was reversed during the AM meal pattern.

Seven days each week, the women walked outdoors for approximately 60 minutes. They also performed five additional bouts of aerobic exercise (treadmill walking or cycling). Each bout burned around 300 calories. Three circuit-training sessions were also included in the program.

At first glance, the results appear to support the popular recommendation to avoid larger meals later in the day, as the greatest weight loss occurred with the large morning meals.

However, the increase in weight loss was actually due to greater muscle loss. Women consuming more calories in the morning lost an extra couple of pounds (1kg) of muscle than subjects consuming the majority of their calories in the afternoon and evening.

What about body fat?

Timing of the meals had no consistent effect on body fat. During the first six weeks of the study, women given the majority of their calories later in the day lost the most fat.

During the second six weeks of the study, there was no statistically significant difference in fat loss between the two groups, although there was a trend towards greater fat loss in women following the AM meal pattern.

When the results from both periods were combined, there was almost no difference in fat loss between the AM and PM meal patterns.

	AM Pattern	PM Pattern
Period 1	– 6.4 pounds	– 8.1 pounds
Period 2	– 5.7 pounds	– 4.4 pounds
Total	– 12.1 pounds	– 12.5 pounds

One of the main limitations with the study is that bioelectrical impedance analysis (BIA) was used to track fat loss and muscle growth.

BIA is not a very reliable way to estimate changes in body composition, with some studies showing that it’s less accurate than BMI [11]. The small amount of muscle loss seen in the AM group could simply be down to measurement error.

That limitation aside, this was a very tightly controlled study. It’s the only meal timing trial to include a structured training program, and does hint at a small advantage to increasing calorie intake towards the end of the day.

Final Thoughts

You can drop fat with a wide variety of diets and meal timing patterns, with your ability to stick to the diet being more important than anything else.

If you find that the conventional “large breakfast and small dinner” advice leaves you hungry, try doing it the other way around. It’s up to you to choose the one that fits your lifestyle. There’s no strong evidence to suggest that either dietary strategy delivers vastly superior results.

As long as you adhere to a few basic dietary guidelines, the way you distribute your calories over the course of the day can be left to personal preference, and won’t have a great deal of impact on your progress one way or the other.