Fasted Cardio vs. Non-Fasted Cardio for Maximum Fat Loss

An article published in The New York Times on December 3, 2019 reported that, “Cyclists who peddled on an empty stomach burned twice as much fat.”

It has been reported in the scientific literature in the past that aerobic exercise after an overnight fast accelerates the loss of body fat. Research has shown that low glycogen and insulin levels from an overnight fast cause your body to shift fuel away from carbs therefore, allowing greater mobilization of stored fat burned for energy. This strategy is basically to help you become a fat-burning machine.

An article published in The New York Times on December 3, 2019 reported that, “Cyclists who peddled on an empty stomach burned twice as much fat.” This study that was reported in the Times’ article was published in the Journal of Clinical Endocrinology and Metabolism. The study found that exercising on an empty stomach before breakfast can lower muscle fat!

The study reported that the aim of the researchers was “to assess acute and chronic effects of exercise performed before versus after nutrient ingestion on whole-body and intramuscular lipid utilization, and postprandial glucose metabolism.”

In a six-week randomized crossover designed controlled trial, researchers at the University of Bath in England recruited 30 overweight, sedentary men. The researchers divided the men into three groups, one as a control and the other two groups riding a stationary bike, three times a week at a moderate pace tracking heart rates as well as the amount of fat that the subjects burn. One exercise group also downed a vanilla-flavored shake two hours before their ride (with no other breakfast) while the other group swallowed a similar-tasting placebo drink, containing water, flavoring and no calories. In other words, the placebo group rode on an empty stomach, but did not know it.

The riders who had pedaled on an empty stomach, however, had incinerated about twice as much fat during each ride as the men who consumed the shake first. The riders all had burned about the same number of calories while pedaling, but more of those calories came from fat when the men did not eat first.

Slimming of Muscle Fat

According to Javier Gonzalez, lead researcher of the study, said, “The reasons for this extra metabolic boost are complex but most likely involve slimming of muscle fat. The fasted riders’ bodies had to turn to internal energy stores for fuel, including fat from their muscles. (Interestingly, the fasted riders did not feel as if their workouts were more draining than the other group, according to everyone’s subjective ratings of their exertions.)”

The results of this study in the Journal of Clinical Endocrinology and Metabolism further confirms the benefits on fasting cardio before breakfast for maximum fat loss! When you eat a meal or carbohydrate before a workout, you increase levels of insulin, which enhances fat storage and inhibition of fat mobilization, oxidation, and fat burning. You do not want to release insulin before cardio if you want to burn more fat. By fasting on an empty stomach before cardio, your body can shift fuels from burning glucose to burning fat. The research shows that fasted cardio before breakfast will not result in loss of muscle tissue to a greater extent than cardio in the fed state.

A June 1, 2018, study published in the International Journal of Exercise Science reported that 10-hour fasting before a resistance training workout enhanced fat oxidation and fat burning. There are only a few studies that looked at the long-term effects of fasted cardio on body composition. The British Journal of Nutrition compared a morning run and eating an early breakfast or while in a fasted state. Not having breakfast resulted in 20% more fat being burned! Another research paper found that cardio-fed or fasted doesn’t make a difference on the amount of fat you lose (J Int Soc Sports Nutr, 2014). What research should we believe?

The scientific research has shown that fasted cardio could be an exciting and promising method for weight loss, fat loss, weight control, and metabolic health. The research shows that for someone with stubborn body fat, as well as someone who is lean, and wants to get ripped, then fasted cardio before breakfast can enhance more abdominal fat and intramuscular fat burning! 

‘The Fat That Makes You Thin’

A study published January 7th, 2021, in the Journal of the International Society of Sports Nutrition, reported that taking caffeine 30 minutes before exercise increased whole-body fat oxidation and fat burning during aerobic exercise.

Caffeine is a powerful central nervous system stimulant that has been shown to increase energy, mental alertness, focus, and exercise performance. It can also reduce appetite and boost metabolism and fat burning. Research has shown that as little as 100 milligrams of caffeine, the amount present in a cup of coffee, can enhance brown adipose tissue (BAT) thermogenesis, and increase energy expenditure.

The widely held belief that all body fat is bad is currently being heavily scrutinized, due to the recent discovery of a different type of fat in humans known as brown fat (BAT). This type of body fat can actually burn off energy in the form of heat by a process known as thermogenesis, which can ultimately reduce overall body fat.

The body has two forms of fat: white fat, or unwanted fat that can lie directly underneath the skin, and brown fat, which often is found in the shoulder blade region or the neck. Unlike white fat, brown fat is the good fat as it can help burn more calories. The more brown fat you have, the more calories you burn. Brown fat is often referred to as “the fat that makes you thin.”

Brown fat is packed with mitochondria loaded with UCP-1, the protein that uncouples fat burning with ATP (energy) production instead of converting the energy into heat via thermogenesis, making the mitochondria effectively the furnace of the cell. The emergence of brown fat as a readily available fat-burning furnace is revolutionary, but like any fire, it requires the proper kindling materials. The ability to get lean by producing extra brown fat, or enhancing the activity of existing brown fat, represents a promising way to burn fat and lose weight.

Several landmark discoveries and approaches to enhancing brown fat function are being explored at major research centers and universities worldwide, with great excitement. Brown fat research is a hot topic today.

 

References:

1. R M Edinburgh, H E Bradley, N-F Abdullah, S L Robinson, O J Chrzanowski-Smith, J-P Walhin, S Joanisse, K N Manolopoulos, A Philp, A Hengist, A Chabowski, FM Brodsky, F Koumanov, J A Betts, D Thompson, G A Wallis, JT Gonzalez. Lipid metabolism links nutrient-exercise timing to insulin sensitivity in men classified as overweight or obese. The Journal of Clinical Endocrinology & Metabolism, October 19, 2019, dgz104, https://doi.org/10.1210/clinem/dgz104

2. Vieira AF, Costa RR, Macedo RC, Coconcelli L, Kruel LF. Effects of aerobic exercise performed in fasted v. fed state on fat and carbohydrate metabolism in adults: a systematic review and meta-analysis. Br J Nutr. 2016 Oct;116(7):1153-1164. doi: 10.1017/S0007114516003160. Epub 2016 Sep 9. PMID: 27609363.

3. Frawley K, Greenwald G, Rogers RR, Petrella JK, Marshall MR. Effects of Prior Fasting on Fat Oxidation during Resistance Exercise. Int J Exerc Sci. 2018;11(2):827-833. Published 2018 Jun 1.

4. Skip Breakfast Before the Gym by Gretchen Reynolds. NY Times. December 3, 2019

5. Gillen JB, Percival ME, Ludzki A, Tarnopolsky MA, Gibala MJ. Interval training in the fed or fasted state improves body composition and muscle oxidative capacity in overweight women. Obesity (Silver Spring) 2013;21(11):2249-2255. doi: 10.1002/oby.20379

6. Horowitz JF, Mora-Rodriguez R, Byerley LO, Coyle EF. Lipolytic suppression following carbohydrate ingestion limits fat oxidation during exercise. Am J Physiol, 1997;273(4 Pt 1):E768-E775

7. Schoenfeld BJ, Aragon AA, Wilborn CD, Krieger JW, Sonmez GT. Body composition changes associated with fasted versus non-fasted aerobic exercise. J Int Soc Sports Nutr, 2014;11(1):54. Published 2014 Nov 18. doi:10.1186/s12970-014-0054-7

8. Paoli A, Marcolin G, Zonin F, Neri M, Sivieri A, Pacelli QF. Exercising fasting or fed to enhance fat loss? Influence of food intake on respiratory ratio and excess post-exercise oxygen consumption after a bout of endurance training. Int J Sport Nutr Exerc Metab, 2011;21(1):48-54

9. Ramírez-Maldonado M, Jurado-Fasoli L, Del Coso J, R Ruiz J, Amaro-Gahete FJ. Caffeine increases maximal fat oxidation during a graded exercise test: is there a diurnal variation? J Int Soc Sports Nutr. 2021 Jan 7;18(1):5. doi: 10.1186/s12970-020-00400-6. PMID: 33413459; PMCID: PMC7792284.

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