Snacking Before Bed Slows Fat Burning, Favors Carbohydrate Oxidation

by Mike Mutzel


Having a bowl of ice cream before bed is not that big of a deal … so long as you’re in a calorie deficit, right?

A new study found that snacks before bed actually slow down fat oxidation overnight by about 15 grams per day.

So, that evening cookie, brownie or ice cream snack could decrease fat oxidation by up to one pound or more per month.

This study, just published last week by scientists at Vanderbilt University, was one of the first of its kind to quantify how eating the same total daily calories—but at different times of the day—impacted metabolism.

It flies in the face of conventional wisdom, which suggests that overall calorie intake is the primary driver of fat oxidation.

Here are a few aspects of this study that make the findings noteworthy:

  • Previous controlled feeding studies in a metabolic chamber wherein meal timing was varied were only 24 hours long. This study was 56 hours long.
  • This was a randomized crossover design study, which means that the study subjects were in both the AM snack group and the PM, albeit at different times.
  • Thirty percent of the subjects were women; most metabolic studies include men predominantly.
  • Total calorie intake and physical activity (steps, etc.) were identical in both the AM snack arm and PM snack arm of the study.
  • When a 700 kcal snack was eaten at 10:00 PM versus at 8:00 AM, overnight fat oxidation was reduced by 15 grams (though carbohydrate oxidation was increased).

This video further explains the above and links back to related articles and videos that we’ve discussed on this topic.


Related Video: Shopping for OMAD Meals (meat eaters only)


1. Kelly KP, McGuinness OP, Buchowski M, et al. Eating breakfast and avoiding late-evening snacking sustains lipid oxidation. Kramer A, ed. PLoS Biol. 2020;18(2):e3000622–16.

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