Do you exercise in the morning on an empty stomach? If so, Nicholas Tiller, PhD, research associate at The Lundquist Institute for Biomedical Innovation, wants you to know the long-term effects of your fasted workout routine. In a recent National Geographic article, Dr. Tiller, alongside other researchers, compares fuel utilization versus fat loss, encouraging a more big-picture way of thinking.
“In a fasted state, lower insulin levels lead to higher rates of lipolysis (the breakdown of fat for energy)”, said Dr. Tiller. He goes on to explain that the body has two fuel tanks: one readily available (from recent food intake) and another in reserve (stored fat). “Exercising while fasted effectively drains the first tank, forcing your body to rely on its backup fuel source—fat,” he added.
However, Dr. Tiller wants you to know that burning more fat during a workout doesn’t equate to losing more body fat overall. It all comes down to calorie balance and the total amount of fat burned over days and weeks, not during a single workout session. Throughout the article, Dr. Tiller and his colleagues also discuss the physiology, metabolic health effects, body composition, and muscle growth, as well as individual differences such as behavioral or lifestyle factors that play a role in fasted exercise.
Curious to know more of what Dr. Tiller advises? The full story is available here via National Geographic (subscription required).