How often you should eat, and when, according to research

Do you have a colleague or friend who's into fad diets? Maybe you’ve noticed that instead of three meals a day, they’re eating six smaller meals.

The internet and our social circles are rife with claims about meal frequency and the correct times to eat throughout the day. Here’s what the most up-to-date research suggests is really best for health.

Six meals a day?

In a study published in Diabetes and Metabolism, researchers compared the effects of eating three meals a day vs six. In both cases, the participants, who either had diabetes or prediabetes, consumed the same number of calories. 

Using a cohort of 47 people who followed the prescribed diets over six months, researchers examined how these two eating patterns affected glycemic control and satiety, as well as factors like body weight. They found that while body weight levels remained stable throughout the study period, participants on the six-meals-per-day regimen saw a decrease in glycated hemoglobin and post-oral glucose tolerance test blood glucose levels, which indicates generally improved blood sugar control. Likewise, that eating pattern led to a decrease in the frequency of abnormally high insulin levels and delayed the time it took for blood glucose to peak following consumption of sugar in prediabetic participants. 

Eating six meals a day also appeared to result in suppressed hunger and appetite in all participants.

“Although weight loss remains the key strategy in hyperglycaemia management, dietary measures such as more frequent and smaller meals may be helpful for those not sufficiently motivated to adhere to calorie-restricted diets,” the authors concluded. “Our study shows that 6 vs 3 meals a day can increase glycaemic control in obese patients with early-stage T2D, and may perhaps improve and/or stabilize postprandial glucose regulation in prediabetes subjects.”

That said, limitations of the study suggest this approach isn’t a weight-loss panacea––and subsequent research has both supported and run contrary to these claims.

The dish on meal frequency

A review published in Nutrients, which focused on the health impacts of meal frequency and timing, illustrates the variable study findings.

For example, the authors cite several studies that showed eating six or more meals a day was associated with lower concentrations of total and low-density lipoprotein cholesterol, compared with those who eat one or two meals a day. Likewise, other studies cited in the review found that splitting daily calories across at least four meals a day led to lower risks of obesity and a smaller waist circumference, compared to three or less.

However, the review also includes studies that show a lower frequency of meals may have a similar impact. One study involving more than 50,000 adult participants found that those who eat one or two meals a day had a lower BMI compared with those who eat three or more each day. The review’s authors noted that while some research suggests that a higher frequency of eating reduces risks of weight gain, others that investigated the acute metabolic responses to differing meal frequencies indicate the opposite. 

Among the confounding factors involved in some of these studies is the nutritional content of what’s being eaten. For example, while the authors cite a study that showed increasing meal frequency resulted in a significant reduction of total and LDL cholesterol, they noted that these participants also reported a reduction of carbohydrate intake.

Likewise, the authors observed that those eating fewer meals a day often eat more irregularly, changing the timing of when they eat and how much. This appears to increase hunger-related hormones, cause weight gain, and lead to metabolic disturbances when compared to low-frequency eating with regular timing.

In fact, the review, along with a growing body of research, suggests that timing may be a far more important consideration than meal frequency. 

Time to eat!

In light of available evidence, the authors of the review above concluded that high frequency of meals results in negligible differences to body weight and composition, in comparison with low frequency. However, they found some evidence suggesting that consuming a greater proportion of calories earlier in the day can be more physiologically beneficial compared with eating a large number of calories late at night. 

According to the review, eating breakfast tends to result in a lower risk of weight gain, whereas those who eat their largest meal at lunch or dinner time have more of a risk of increasing their BMI. Additionally, evidence suggests that those who skip breakfast can increase their risk of coronary heart disease (CHD) by as much as 27%, and eating the majority of daily calories late at night can increase CHD risk by as much as 55%. 

“Both dinner and breakfast skipping increased 24-h energy expenditure, concomitant with a longer fasting period, but skipping breakfast may elicit higher postprandial insulin concentrations and increased fat oxidation, suggesting a metabolic inflexibility that may lead to low-grade inflammation status and impaired glucose homeostasis,” the authors wrote.

Much of this is related to the peripheral tissue clocks that are a part of the overall internal circadian clock. These are involved in metabolic rhythms like glucose and lipid regulation. For example, the gut’s peripheral clock regulates glucose absorption; peripheral clocks in adipose tissue and the liver control insulin tissue sensitivity; and the peripheral clock in the pancreas dictates insulin secretion.

Research shows that this can lead to poorer glycemic control during evenings and nights in healthy adults, which means those who eat a large meal later in the day do so during a period of low glucose tolerance. On a similar note, studies have shown that those who eat most of their calories during periods close to the release of melatonin (the biological marker for onset of impending sleep) are more likely to be obese. 

Bottom line

So when should you eat and how often? Here are two key takeaways. First, the current research suggests that eating most of your calories earlier in the day produces the most benefits for health. Second, eating meals at regular times can help keep these peripheral clocks synchronized with your behaviors. 

Regardless of how many meals you decide to eat, stay regular and don’t skip breakfast.