Study under review: A Smartphone App Reveals Erratic Diurnal Eating Patterns in Humans that Can Be Modulated for Health Benefits
The “city that never sleeps” may have originally referred to New York City, but cable television, the Internet, and countless 24-hour food options have allowed people in nearly any city to live a 24/7 lifestyle. Along with this lifestyle comes a greater likelihood of eating increasing amounts of food later in the evening.
Among the many reasons this can impact weight gain are the effects of food timing on thermogenic response to a meal. These effects are due to circadian rhythms, or our internal body clock, which synchronize the daily patterns of metabolic activities such as when we sleep and wake up, when we eat, and changes in hormone levels. These rhythms, which occur in nearly every species, allow an organism to predict environmental changes and optimize activity, sleep, and food intake patterns throughout the course of a day. There are a few temporary exceptions to animals having a strong rhythm. These include egg-laying ant queens and bee queens, as well as some migrating animals and animals, who spend time in complete darkness either underground or at the North and South Pole. Human exceptions though are rarely due to nature, and more often due to society and technology.
How our bodies respond to food intake is highly dependent on timing, thanks to our internal body clocks. Normally, the human body is prepared for activity and food ingestion during daylight hours and for rest and fasting during darkness. For example, during the day, the liver increases the expression of enzymes involved in storing carbohydrate, while at night the liver favors breaking down carb stores to maintain healthy blood sugar levels during the overnight fast. Although it is also important to efficiently switch from carb breakdown during fasting to carb storage after a meal, from an evolutionary and energetic perspective, it would not be advantageous to express the opposite enzymes (glycogen synthase and glycogen phosphorylase) at high levels throughout the day. Daily fluctuations in transporters for glucose, fructose, and amino acids also indicate that the metabolism of carbohydrate and protein is regulated to maximize absorption during normal mealtimes.
A number of animal studies have found significant differences in metabolic responses to eating within an eight to 12 hour eating window, compared with eating throughout 24 hours, even without altering the quality or quantity of the diet. As you may remember from the rodent study in Study Deep Dives #3, time-restricted feeding patterns support an improved circadian rhythm and are associated with improved body composition, increased endurance, and reduced systemic inflammation, as well as improvement in other biomarkers of metabolic disease. Although the animal research on time-restricted feeding windows is very compelling, there is currently very little human research available. The majority of research that has considered the timing of meals has focused on night-shift workers, meal frequency, and people with night-eating syndrome, but not very much has been done in healthy, free-living adults.
Analyzing the timing of a person’s self-selected meal patterns is complicated by a number of logistical issues. Methods of data collection can include the use of subjective questionnaires (often during larger studies), food diaries (that provide constant and potentially behavior-changing feedback to the subject), and in-lab video recording that would obviously not reflect the typical food choices of a participant when they’re at home. However, the widespread use of smartphones provides a great new opportunity for researchers to monitor human behavior across a diverse population.
With this in mind, researchers at the Salk Institute near San Diego developed a phone app that enabled them to measure the natural daily eating patterns of free-living healthy adults, while providing minimal feedback to the users. After collecting the data, a pilot feasibility study was undertaken to determine whether reducing the daily eating interval to 10–12 hours without any other attempts to change dietary intake could lead to weight loss in overweight but otherwise healthy individuals.
Circadian rhythms influence the body’s response to a meal. Animal studies have shown that restricting food intake to a window of eight to 12 hours can lead to improved health, although few human studies exist. The use of smartphone apps can aid researchers in tracking eating patterns of free-living adults across a variety of demographic populations. Researchers developed a phone app that enabled them to record the self-selected daily eating patterns of free-living healthy adults.
Other Articles in Issue #13 (November 2015)
What are you feeding your bacteria?
While probiotics get most of the press, prebiotics arguably have more potential for altering one’s microbiome. This study looks at a promising type of prebiotic supplement to see if it might impact appetite and inflammation.
Breakfast: A disempowering nutritional dogma
By Martin MacDonald, Msc
Return of the globule: milk fat strikes back
Milk fat is structurally different than most other fats, and the milk fat globule membrane has been looked at previously (twice in Study Deep Dives, in fact) for its impact on chronic disease. But could it also impact response to exercise?
Studies have shown that supplement buyers generally trust the supplements they buy. That might not be the safest assumption, as dietary supplements that are presumed helpful or neutral may sometimes cause serious side effects, as quantified by this study.
Probiotics and the propensity for portliness
When you eat a meal, your gut bacteria also eats a meal. And gut bacteria are increasingly looked at for their influence on chronic disease. This study looks at the effect of a specific probiotic blend on weight gain.
The espresso effect: caffeine and circadian rhythm
Your daily rhythms are influenced by “zeitgebers” such as light and exercise. But until now, we haven’t known the exact impact of late-day caffeine intake on melatonin and circadian rhythms.
Money, time, and the science that suits us
By David Katz, MD, MPH
Does marijuana actually boost creativity?
Ancedotally, weed has been claimed as a creativity booster for decades. With THC having an effect on dopamine, a plausible mechanism exists. This randomized trial puts marijuana to the test.
Diet and autism: no gluten, no casein, no difference?
Gluten and casein are two food components often linked with autism spectrum disorder symptoms. Hence the prevalance of wheat and dairy free diets. But will they work in a rigorously controlled trial?