If you ate a high-carb meal at breakfast, then had the same meal for dinner, your body would not turn more carbs into fat after dinner than it would at breakfast. But as you probably suspect, the answer is not that straightforward. While the time of day doesn't automatically result in converting more carbs into fat, the fate of the carbs you consume at dinner can be changed by a few variables.
Fate of Carbs
Carbs are the primary source of fuel for your body, so after they're digested they go to cells everywhere in your body. If you consume more calories than you need for energy, extra carbs are stored as glycogen in your liver and muscles. Under normal circumstances, they're converted into triglycerides and stored as fat only after your metabolic needs are met and glycogen stores are full. If you're active and consume the right amount of calories, little to no carbohydrate is stored as fat, reports Columbia University. The time of day you eat does not affect whether calories from carbs become fat.
Type of Carb Matters
The type of carb you consume can increase the chance of carbs becoming fat. If you eat processed carbs, such as white rice and white bread, have a baked potato, or consume too much added sugar from baked goods or sweetened beverages, your blood sugar will dramatically increase. This triggers the release of insulin, which has one job: to get blood sugar back to normal. Insulin tries to transport all of the sugar to cells for energy, but if there is too much in your blood, it tells your liver to begin turning sugar into triglycerides. As a result, the carbs you have for dinner may be stored as fat.
Calories Burned While Sleeping
Even if you eat dinner close to bedtime, carbs are still used for energy to support your brain, heart and other vital functions while you sleep. The metabolic rate goes down by about 15 percent during sleep, according to an August 2010 report in the "International Journal of Endocrinology." But the sleeping metabolic rate, which determines the amount of carbs burned while sleeping, varies depending on your weight. The average sleeping metabolic rate is lower than the normal resting metabolic rate, or RMR, in people who are overweight, but it's higher than the RMR in others, concluded a study in the "International Journal of Obesity and Related Metabolic Disorders" in March 2002.
Carbs at Dinner and Weight
One research study found that eating most of your carbs at dinner does not cause weight gain. It may even support weight loss. In the study, two groups of men followed similar low-calorie diets, but one group ate most of their carbs at dinner. Men with the high-carb dinners lost more weight and more fat around their waist compared to the other group, according to the study published in the journal "Obesity" in October 2011. The same researchers later reported in "Nutrition, Metabolism and Cardiovascular Disease" that eating carbs at dinner influenced levels of appetite-regulating hormones during the day, which may prevent feeling hungry in the middle of the day.
- Columbia University: Does Carbohydrate Become Body Fat?
- NYU Langone Medical Center: True or False? Eating at Night Will Make You Gain Weight
- Colorado State University: Physiologic Effects of Insulin
- International Journal of Endocrinology: Sleep and Metabolism: An Overview
- International Journal of Obesity and Related Metabolic Disorders: Sleeping Metabolic Rate in Relation to Body Mass Index and Body Composition
- Obesity: Greater Weight Loss and Hormonal Changes After Six Months Diet With Carbohydrates Eaten Mostly at Dinner
- Nutrition, Metabolism and Cardiovascular Diseases: Changes in Daily Leptin, Ghrelin and Adiponectin Profiles Following a Diet With Carbohydrates Eaten at Dinner in Obese Subjects
- Iowa State University Extension: Carbohydrate