Physiologist Ancel Keys reportedly told Vogue magazine in 1956 that “localized fat reduction” was possible (1): Great news! Five years later, Keys told Time magazine that smoking didn’t have a measurable impact on coronary heart disease. (2) Bit of a blunder, that.
Dr. Keys was something of a pioneer with regard to the hazards of excessive fat intake, (3) but science is a fickle bugger. Half a century on, I think it’s safe to say that most contemporary trainers and dietitians would scoff at his claims about spot fat loss.
Spot reduction is considered too good to be true. But if you pry open the existing (and emerging) literature or listen to what some of the sharpest minds in exercise science have to say, it kind of seems like spot fat reduction isn’t just possible, but something that happens all the time. Here are the caveats: “spot reduction” may be a misnomer, and you probably don’t have too much control over it.
Fat Loss, Explained
First, let’s briefly brush up on our physiology. Here’s how your body manages its fat reserves, in descending order of complexity:
- Chronic energy surpluses facilitate a process known as de novo lipogenesis, during which excess carbohydrate in the bloodstream is converted into fatty acids that are then esterified into storage triacylglycerols. The body will then β-oxidate stored fatty acids into usable energy on an as-needed basis through a mechanism known as gluconeogenesis. (4)
- When you habitually ingest more energy from food than you expend through activity, your body will regulate that excess energy by converting it into a form that can be stored inside new or existing fat cells. In conditions of energy deprivation, metabolic signals influence the utilization of existing fatty acids, which are converted into readily usable energy.
- When you eat more than your body needs, you gain fat. When you eat less than you need, you burn fat.
[Related: The Best Calorie Calculator on the Internet]
Okay, Then What Is Spot Fat Reduction?
Spot reduction implies that you can intentionally burn fat from specific body parts through your diet or exercise choices. While there’s more to that idea than you might think, a better descriptor of this phenomenon might be localized fat reduction — body-part-specific fat loss that occurs independent of a person’s dietary or activity choices. Local fat loss happens all the time, but spot reduction was thought to be a myth.
[Read More: The Fat Loss Myth You Want to Be True: Spot Fat Reduction]
Studies Show Spot Fat Reduction Exists…
In a March 20, 2024 episode of the Stronger by Science Podcast, some of the smartest guys in health science got together to discuss how compelling the data on spot reduction actually is. Co-hosts Greg Nuckols, Milo Wolf, and Pak Androulakis-Korakakis (“Dr. Pak”) discussed the trend’s surprisingly long history.
- In 1965, Mohr observed “significant reductions in girth at the waistline” following a cluster of six-second isometric abdominal contractions, “despite no appreciable change in weight.” (5)
The paper’s design is flawed by modern scientific standards. Nuckols quibbled with it, saying, “…if you could meaningfully spot-reduce in 30 seconds of exercise per day, the world would look very different.” Moreover, it strains credulity to imply that participants lost inches off their waists without their scale weight changing “appreciably.” Studies conducted post-Y2K hold more water:
- A 2017 paper by di Palumbo et al. alleges that “explosive resistance exercise prior to a bout of endurance training … may elicit localized fat mass loss.” (6)
Dr. Pak noted that this study didn’t instruct participants to make any changes to their dietary habits, including intentionally entering a calorie deficit — something almost universally considered essential for weight loss.
- A boldly-titled study from 2023 (“Abdominal aerobic endurance exercise reveals spot reduction exists”) claimed in its abstract that, “Abdominal endurance exercise utilized more local fat than treadmill running, indicating that spot reduction exists in adult males.” (7)
The SBS guys regarded that rhetoric as a bit of a logical leap. Dig deep enough into PubMed, and you can find a paper that backs up just about any health or fitness claim you want. That said, there’s enough data on spot reduction to indicate it’s not a myth after all.
[Opinion: Long-Length Partials Are Overrated for Bodybuilding]
The Stronger by Science podcast is run by bonafide experts who do this topic real justice. If you’re a fiend for the nitty-gritty, you can find the episode on spot reduction here.
…But You (Probably) Can’t Control It
After listening to the SBS discussion, I came away with a new perspective. Conventional wisdom suggests the human body pulls from its fat stores all over, not from one area after another (spoiler; that’s mostly true). Yet I was struggling to split the difference between “intentional spot reduction” and “happenstance body-part-specific fat loss,” so I tapped Nuckols, a frequent BarBend Expert, for his take:
“I think something like ‘inhomogeneous fat loss’ would be a better term. The desire for spot fat reduction is a desire to direct that process,” Nuckols says — a characteristically nuanced answer from a scientific professional.
The desire for spot fat reduction is a desire to direct where and how a person loses fat.
Greg Nuckols, Stronger by Science
Some research hints that you may be able to influence which fat stores your body pulls from. Based on Nuckols & Co’s interpretation of the literature, it might have to do with local blood flow encouraging lipolysis (turning stored fat into a usable form of energy) in the areas surrounding the muscles you’re working.
- Nuckols notes that this effect seems to occur long after you finish your workout. (8) That doesn’t necessarily mean training your abs will encourage body fat utilization from that area exclusively.
[Read More: The Best Ab Exercises, Plus 4 Ab Workout Routines From a Trainer]
Throughout our exchange, Nuckols remarked that the order in which the body pulls from its various fat deposits is largely determined by factors such as hormonal signaling. These signals likely supersede whatever influence your ab workouts may or may not have on your belly fat.
I also asked about stubborn fat. Bodybuilders often struggle to lose fat from areas like the abdomen or lower back; a physique athlete undergoing contest prep may have diced arms and an upper back that looks like a topographic map, but they still hold a bit of pudge in their stomachs that doesn’t vanish until they’re bathing in self-tanner days before their show.
To me, that sounds a lot like spot — or, rather, sequential — fat reduction. Nuckols’ working theory is that those areas may be “poorly vascularized” or less sensitive to the aforementioned hormonal signals. He stressed that he didn’t have data on hand to back these ideas up.
- Nuckols & Wolf also theorized that training a muscle may encourage the body to pull from fat stores around that muscle to repair it and facilitate hypertrophy. Wolf specifically shouted out that what studies classify as “local fat loss” may be more accurately described as “local body recomposition.”
- Dr. Pak: “I think what we’re seeing is untrained individuals experience increases in muscle mass and reductions in body fat at the same time. We must be cautious about the conclusions we draw [from spot fat reduction studies].”
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Hitting the Spot
All told, it seems like spot fat reduction definitely happens. Nuckols et al. aren’t totally moved by recent papers, despite having a few different hunches on how things work under the hood. You might slightly accelerate how fast your body burns off its belly fat if you perform high-rep ab workouts regularly, but experts aren’t ready to go all-in on that idea just yet.
So how did we land on spot fat reduction being a myth in the first place? I think there’s a pretty plausible pipeline:
- “Paul” wants to lose a bit of belly fat and starts performing ab workouts at home or in the gym.
- Motivated by his workouts (cheers, endorphins), Paul subconsciously starts making healthier choices in the kitchen and enters a slight calorie deficit in the process.
- If Paul’s new to exercise, his abs might undergo some hypertrophy, even though he isn’t bulking up. (9)
- With enough time and dedication, Paul drops some body fat and his abs start feeling stronger and more pronounced.
Ipso facto, Paul concludes the changes in his body composition resulted mainly from exercising the area he wanted to improve. Is that what happened? Perhaps partially, if the idea that regional blood flow facilitates local fat loss bears out.
Realistically, Paul made a series of healthy behavior changes, stuck to them, and his body eventually tapped into the fatty reservoirs around his midsection. “Spot fat reduction” occurred, but Paul didn’t cause it.
Nuckols bottled his thoughts on the podcast like this, which he echoed to me as well: Spot fat reduction (or, rather, inhomogeneous fat loss) is real, but it doesn’t seem to be influenced by specific diet or exercise behaviors. At least, not significantly at this time.
Did Dr. Keys lie to Vogue and/or Time? No, at least likely not with malicious intent. The scientific method is imperfect. Researchers take shots on goal over the course of decades, hoping to eventually land on a valuable and practical approximation of a complicated topic.
Many of the purported explanations for spot fat loss are things most people should do anyway when trying to lose weight, such as training their abdominal muscles, eating heaps of protein, and simply being patient. Best-case scenario? If these studies are on the mark, spamming crunches or ab circuits might actually carve out your six-pack a little bit quicker.
If the data is off about spot fat loss and it falls entirely under the jurisdiction of genetics (and time), it’s not like you’ve done yourself any harm along the way.
References
- Paoli A, Casolo A, Saoncella M, Bertaggia C, Fantin M, Bianco A, Marcolin G, Moro T. Effect of an Endurance and Strength Mixed Circuit Training on Regional Fat Thickness: The Quest for the “Spot Reduction”. Int J Environ Res Public Health. 2021 Apr 6;18(7):3845.
- Time Inc. (1961, January 13). Medicine: The fat of the land — printout -. Time.
- Kim, Y., Je, Y., & Giovannucci, E. L. (2021). Association between dietary fat intake and mortality from all-causes, cardiovascular disease, and cancer: A systematic review and meta-analysis of prospective cohort studies. Clinical nutrition (Edinburgh, Scotland), 40(3), 1060–1070.
- Ameer, F., Scandiuzzi, L., Hasnain, S., Kalbacher, H., & Zaidi, N. (2014). De novo lipogenesis in health and disease. Metabolism: clinical and experimental, 63(7), 895–902.
- Mohr, D. R. (1965). Changes in Waistline and Abdominal Girth and Subcutaneous Fat following Isometric Exercises. Research Quarterly. American Association for Health, Physical Education and Recreation, 36(2), 168–173.
- Scotto di Palumbo, A., Guerra, E., Orlandi, C., Bazzucchi, I., & Sacchetti, M. (2017). Effect of combined resistance and endurance exercise training on regional fat loss. The Journal of sports medicine and physical fitness, 57(6), 794–801.
- Brobakken, M. F., Krogsaeter, I., Helgerud, J., Wang, E., & Hoff, J. (2023). Abdominal aerobic endurance exercise reveals spot reduction exists: A randomized controlled trial. Physiological reports, 11(22), e15853.
- Merlotti C, Ceriani V, Morabito A, Pontiroli AE. Subcutaneous fat loss is greater than visceral fat loss with diet and exercise, weight-loss promoting drugs and bariatric surgery: a critical review and meta-analysis. Int J Obes (Lond). 2017 May;41(5):672-682.
- Slater GJ, Dieter BP, Marsh DJ, Helms ER, Shaw G, Iraki J. Is an Energy Surplus Required to Maximize Skeletal Muscle Hypertrophy Associated With Resistance Training. Front Nutr. 2019 Aug 20;6:131.
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