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Have you heard of the term "circadian metabolism?"

I just ran across it skimming through a study that looked into whether or not the timing of a mouse’s meals had an effect on its body weight (more on this later). Essentially, animals have an endogenous clock within their bodies that responds to environmental light-dark cycles. This "clock" is not just a part of our brains (which is how I always thought about circadian rhythms in general), it is also a part of the peripheral tissues (e.g., liver, intestines, and fat) that determine how animals use the nutrients and energy they (we) take in. The clock exerts its effect by modulating the expression and activity of enzymes that are involved in metabolic processes.

This concept has led researchers to ask whether when animals eat affects what eventually happens to what they eat. It’s a reasonable question since different metabolic pathways are most active at different times of the day.

Back to the paper on mice. Scientists had found that feeding an ad libitum (i.e., free feeding), high fat diet to mice "disrupted the circadian expression of metabolic factors" and led to obesity. In this study, the researchers determined that timing the feedings of a high-fat (HF) diet more or less eliminated its harmful effects:

Although timed HF-diet-fed& mice consumed the same amount of calories as ad libitum low-fat diet-fed mice, they showed 12% reduced body weight, 21% reduced cholesterol levels, and 1.4-fold increased insulin sensitivity. Compared with the HF diet ad libitum, the timed HF diet led to 18% lower body weight, 30% decreased cholesterol levels … and 3.7-fold improved insulin sensitivity … Taken together, our findings suggest that timing can prevent obesity and rectify the harmful effects of a HF diet.

This correlates well with a study in people that received wide-spread attention in January of this year. Paraphrasing the paper’s abstract:

Participants were grouped in early eaters and late eaters, according to the timing of the main meal (lunch in this Mediterranean population). 51% of the subjects were early eaters and 49% were late eaters (lunch time before and after 1500 hours [3 p.m.], respectively). Late lunch eaters lost less weight and displayed a slower weight-loss rate during the 20 weeks of treatment than early eaters. Surprisingly, energy intake, dietary composition, estimated energy expenditure, appetite hormones and sleep duration was similar between both groups. Nevertheless, late eaters were more evening types, had less energetic breakfasts and skipped breakfast more frequently that early eaters (all; P<0.05). Eating late may influence the success of weight-loss therapy.

Neither of these papers directly addresses the question of whether when a dog eats could improve his chances of losing weight. (That would be a fantastic study … any takers out there?) But, if you are feeding your overweight dog an appropriate number of calories and are not seeing the expected results, changing when you feed would certainly be worth a try. Start by feeding most of the calories early in the day, and if an evening meal is necessary for behavioral reasons, keep it as small as possible.

Dr. Jennifer Coates


Timed high-fat diet resets circadian metabolism and prevents obesity. Sherman H, Genzer Y, Cohen R, Chapnik N, Madar Z, Froy O. FASEB J. 2012 Aug;26(8):3493-502.

Timing of food intake predicts weight loss effectiveness. Garaulet M, Gómez-Abellán P, Alburquerque-Béjar JJ, Lee YC, Ordovás JM, Scheer FA. Int J Obes (Lond). 2013 Jan 29.

Image: Suslik1983 / via Shutterstock

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