Eat a Big Breakfast – Not a Big Dinner

Eat a Big Breakfast – Not a Big Dinner!

A calorie is not just a calorie. It depends when we eat them!

Calories eaten in the morning are less fattening than those eaten later in the day. More calories are burned off in the morning due to diet-induced thermogenesis, which is the amount of energy the body takes to digest and process a meal, given off in part as waste heat. If you eat the exact same meal in the morning, afternoon, and night, our body uses about 25% more calories to process it in the afternoon than in the evening, and about 50% more to digest it in the morning. leaving fewer net calories in the morning to be stored as fat.

A group of researchers randomly selected 20 people to eat the same standardized meal at 8 am or at 8 pm. A week later, the researchers had them come back at the opposite time, so each person ate the same meal for breakfast and for dinner. After each meal, the subjects were placed in a calorimeter (a device that measures the amount of heat [calories] released or involved in a chemical reaction) to precisely measure how many calories were being burned over the next three hours. The meal given in the morning took about 300 calories to digest, while the same meal given at night used up only about 200 calories to digest. The meal itself was about 1,200 calories. Same meal, same food, same amount of food, but effectively 100 less calories.

Harvard researchers randomly selected individuals eating identical meals at 8am versus 8pm while under simulated night or day shifts. Regardless of their activity level or sleeping cycle, calories burned processing the morning meals were 50% higher than in the evening. The difference is explained by chronobiology –it’s part of our circadian rhythms to burn more meal calories in the morning.

When we eat in the morning, our body bulks up our muscles with glycogen, the primary energy reserve used to fuel our muscles. But this takes energy. In the evening, our body expects to be sleeping for much of the next 12 hours. Rather than storing blood sugar as extra glycogen in our muscles, it preferentially uses it as an energy source, meaning we burn less of our backup fuel (body fat). In the morning, our body expects to be running around all day, so it continues to dip into its fat stores while we use breakfast calories to fill our muscles with the energy reserves needed to move around over the course of the day.

More calories are used to process a morning meal because instead of just burning glucose (blood sugar) directly, our bodies use up energy to string glucose molecules together into chains of glycogen in our muscles, to be broken back down into glucose later in the day. That extra assembly/disassembly step takes energy—energy that your body takes out of your meal, leaving you with fewer calories.

Our muscles are particularly sensitive to insulin in the morning, rapidly pulling blood sugar out of our bloodstream to build up glycogen reserves. At night, our muscles become relatively insulin resistant and resist the signal to take in extra blood sugar. That means you get a higher blood sugar and insulin spike in the evening compared to eating the exact same meal in the morning. In that 100-calorie difference study, blood sugars rose twice as high after the 8pm meal compared to same meal in the morning. Shifting the bulk of our calorie intake towards the morning would appear to have a dual benefit—more weight loss, and better blood sugar control.

For the source of this information, watch the 5.75-minute video https://nutritionfacts.org/video/eat-more-calories-in-the-morning-than-the-evening/