Does Dinner Time Affect Your Weight?

You have likely heard that eating dinner late can be bad for your health, raising the risk of weight gain. But in reality, the association between meal timings and circadian rhythm is still not completely clear to us.

Most of the studies linking late dinner with weight gain are observational which means that several factors aside from timing could play a role — physical activity, smoking status, quality of sleep, and alcohol consumption to name a few. 

Rather than when you eat, some nutrition experts argue that what you eat and how much you eat matter a lot more for your waistline. 

"I recommend not having large amounts of carbs–otherwise that carb turns into sugar in your blood and you get a rise in insulin," registered dietitian Alissa Rumsey told Elle. "Since you are just going to bed, you aren't using that sugar for energy, so you're more likely to store it as fat."

In a new observational study from Okayama University, Japan, researchers reported no evidence to suggest that a two-hour long interval between dinner and bedtime could affect HbA1c levels. It is worth noting that a typical Japanese diet is rich in vegetables and small in portion sizes. 

On the other hand, a typical American diet may include food options that are processed and contain added sugars i.e. foods more likely to contribute to weight gain. This could explain why the findings of the Japanese study are different from Western studies.

Regarding the factor of portion size, you will need to ensure that you eat right during other meals of the day. If you are prone to skipping or not eating enough of daytime meals, it is likely that you may overeat during your last meal of the day or take up junk food snacking.

Again, the additional calorie intake here is what causes weight gain according to celebrity trainer Jillian Michaels. "As long as you don’t overeat, you won’t gain weight no matter when you consume your calories," she suggests.

One study from 2013 revealed how those who ate a bigger breakfast (compared to dinner) were more likely to manage their weight than those who ate bigger dinners. The former group also had better results in terms of their fasting glucose, insulin, and hunger.

"So how can we assess these claims about when to eat? Actually, the truth is that one diet message does not fit all people," Alex Johnstone and Peter Morgan, nutrition experts from the University of Aberdeen, wrote for the Conversation.

So while many dietitians recommend a two-hour interval between dinner and sleep, it is best to consult a registered dietitian who will help you take individual factors into account.

"Some people will be able to control body weight better with a big breakfast and some with a large evening meal. You can assess your own biological bias," Johnstone and Morgan added.