In the early 1970s, meals made up 82% of adult calorie intake and snacks contributed 18%. Fast-forward to today, and meals make up 77% of calories while snacks contribute 23%.
We’re eating more frequently throughout the day, and in fact a recent study showed that healthy, non-shift-working adults eat an average of 4.2 to 10.5 times per day. The only time <1% of the people surveyed don’t eat is from 1am to 6am. Because the times of day and night that we eat affect our body’s circadian clock rhythm, which regulates all aspects of metabolism, meal timing can have serious implications for the development of cardiovascular disease (CVD), type 2 diabetes, and obesity.
The American Heart Association (AHA) recently released a scientific statement that reviews the cardiometabolic health effects of specific eating patterns: skipping breakfast, intermittent fasting, number of daily eating occasions, and timing of meals and snacks.
Here is what they found:
The AHA defines breakfast as the first meal of the day eaten within 2 hours of waking up, typically somewhere between 5am and 10am. Fewer adults today eat breakfast, which coincides with the increase in obesity. Also, the Bogalusa Heart Study showed that 74% of breakfast skippers did not meet two-thirds of the Recommended Dietary Allowance for vitamins and minerals compared with 41% of those who consumed breakfast. People who routinely skip breakfast are also more likely to have higher blood sugar levels and increased risk of developing type 2 diabetes, high blood pressure, and elevated cholesterol levels. While there is an association between skipping breakfast and obesity, recent research shows that eating breakfast has a limited effect on weight loss, probably because people today tend to eat numerous times throughout the day and the total daily calorie intake and food choices have a greater impact on weight than breakfast alone.
Defining lunch, dinner and snacks:
The AHA concludes that using time of day to define lunch and dinner isn’t appropriate because there are cultural differences. According to 2004 data from the Bureau of Labor Statistics, almost 15 million Americans work full time on evening shift, night shift, rotating shifts, or other employer arranged irregular schedules that impact meal timing. Is it ‘lunch’ if someone sleeps during the day and eats their meal at midnight? The AHA defines meals as containing at least 210 calories and any eating occasion with less than 210 calories as a snack. Eating more meals and fewer snacks is associated with healthier food choices that include more fruit, vegetables, whole grains and lean protein sources.
Is it better to eat three meals per day, or to eat several small meals and/or snacks throughout the day? The AHA concludes that there isn’t enough evidence to prove that changing the number of times we eat has a significant impact on weight or CVD risk factors such as blood pressure, triglycerides, cholesterol, and blood sugar levels. The key isn’t the number of times we eat, but rather what we choose to eat. Consuming an overall healthy variety of foods that include fruits, vegetables, whole grains, and lean protein sources; and eating fewer processed foods higher in sodium, fat and calories is a well-known way to improve health, no matter how many times per day we eat.
Eating late at night, defined as within 2 hours of going to bed, seems to increase CVD risk. People who work the midnight shift and eat during times that most people are asleep tend to have higher blood sugar, cholesterol and triglyceride levels. Disruption of circadian rhythms appears to be at least partially responsible for the increased cardiovascular risk of eating late in the evening. The recommendation to eat like a king at breakfast, like a queen at lunch, and like a pauper at dinner may have scientific merit. Some studies show that eating the largest meal of the day later in the evening, instead of during the day, increases cardiometabolic risk factors. Timing meals and snacks to fit within 10-12 hours, such as between 6am and 6pm, may help promote weight loss as well as decrease cardiovascular risk.
There is increased interest in intermittent fasting both to lose weight as well as improve overall health. The two most common forms of intermittent fasting include alternate-day fasting and periodic fasting. Alternate-day fasting involves a “fast day,” consuming ?25% of baseline calorie needs during a 24-hour period, alternated with a “feast day,” when participants eat as much as they like. Periodic fasting involves fasting one or two non-consecutive days per week, with unlimited food choices the rest of the week. Research on both types of fasting shows that participants typically lose 3-8% of their body weight after 3-24 weeks of following a fasting program. The impact on health parameters, however, is variable. Some studies show a decrease in total cholesterol and LDL cholesterol, and others report no effect. Triglyceride levels decrease along with weight loss; the more weight people lose, the lower their triglyceride levels. Blood pressure levels decreased only in people who lost 6-7% of their body weight, and insulin resistance decreased when people lost at least 4% of their body weight.
The AHA scientific statement encourages an intentional approach to eating:
- Plan meals and snacks for specific times throughout the day to manage hunger.
- Limit meals and snacks to a 10-12 hour timeframe during the day, avoiding eating later in the evening. For example, eat only between 6am and 6pm, or between 7am and 5pm.
- Choose meals and snacks that contain a variety of nutrient-dense, healthy foods instead of relying on packaged and processed snack foods.
- Consume a larger proportion of calories earlier in the day, making breakfast, lunch and daytime snacks higher in calories than dinner and evening snacks.
- Consider using an intermittent fasting approach to decrease calories and lose weight, which may also decrease cardiovascular and diabetes risk.
By Lynn Grieger, RDN, CDE, CPT, CHWC
- St-Onge MP, Ard J, Basin ML, Chiuve SE, Johnson HM, Kris-Etherton P, Varady K; American Heart Association Obesity Committee of the Council on Lifestyle and Cardiometabolic Health; Council on Cardiovascular Disease in the Young; Council on Clinical Cardiology; Stroke Council. Meal Timing and Frequency: Implications for Cardiovascular Disease Prevention: A Scientific Statement From the American Heart Association. Circulation. 2017 Feb 28;135(9):e96-e121. doi: 10.1161/CIR.0000000000000476. Epub 2017 Jan 30.
- Bureau of Labor Statistics. Economic News Release. Workers on Flexible and Shift Schedules in 2004. https://www.bls.gov/news.release/flex.nr0.htm Published 7-1-2005. Accessed 10-12-2017.
PDF Handout: Meal Timing Handout