I Want to Lose Weight! Should I Focus on Diet or Exercise?

Kale or kettlebells?

No question in the fitness world is so freighted with misunderstanding and laden with disappointment. No question evokes so much tsuris.

It is, of course, the completely wrong question. Fitness and health isn't a zero-sum game where you can focus solely on one category and blithely ignore the other. There aren't too many high caliber athletes who subsist on Twinkies and beer. Conversely, show me a person that never moves and restricts their calories, and I'll show you a person that's not healthy.

And it gets more complicated and nuanced. Take your average super-skinny supermodel and a very active middle-aged athlete with a paunch. Is it possible that the supermodel has more body fat than the middle-aged athlete even though the middle-aged athlete weighs more? Yes, it's possible. Muscle is about 13 percent denser than fat, and one liter of muscle weighs about 0.3 pounds more than one liter of fat. Furthermore — and perhaps more importantly — the middle-aged athlete with the paunch will almost certainly be fitter and have a greater chance of longevity.

Numerous studies have demonstrated the importance of exercise and physical conditioning in promoting longevity. A recent study cited in Nature was unequivocal in its findings, stating that "Our data also suggest that a further increase in physical activity level, achieved through regular exercise training, can largely negate the effects of aging." (1)

And then there's my favorite health study of all-time: the "Double-Decker Bus Survey." I've written about this study before. You can read about it here: https://beneath-the-skin.ghost.io/n-e-a-t-2/ The study famously showed that the number one factor in avoiding cardiovascular disease was movement.

So, in conclusion, it's not possible to diet your way into health, fitness, and longevity. You have to move.

Here comes a controversial take — albeit one formed by twenty years of experience in the fitness and health industry. Weight loss should not be the primary concern for exercising. That statement may sound like it's tantamount for career suicide, but I believe it's absolutely true. Exercise accrues many benefits, including mental health, strength, flexibility, balance, and longevity. It might include fat loss as well.

But most people underestimate how hard (and often) they have to work out to treat exercise as a conduit to fat loss. I've written about this topic before: https://beneath-the-skin.ghost.io/epoc-the-loch-ness-monster-of-fitness/

It's best to treat weight (fat) loss as a peripheral benefit to exercising, rather than the main goal. Flipping the calculus is often a recipe for disappointment.

So, with all those caveats out of the way, we still have the question that inaugurated this article: is diet or exercise more beneficial for weight loss?

To best answer that question, let's take three hypothetical individuals: Harry, Barry, and Larry. (Feel free to substitute "Sherry, Mary, and Carrie.")

Harry is very overweight, to the point where he's physically not capable of moving very much. Harry's experience is outside the purview of this article. He would certainly benefit from both extra movement and a nutrition program (with licensed and trained professionals) and perhaps medical intervention as well.

Larry is in very good shape. He works out hard and tries to pay attention to his eating regimen. But, that last five or ten pounds is really hard to lose! My advice to Larry is very succinct: forget about it! The human body fluctuates between three to five pounds daily. Trying to lose that "magical" five pounds is a fool's errand.

Which brings us to Barry. Barry used to play sports and hit the gym on a pretty regular basis. But then he graduated from college, joined the work force, and had a few kids. Next thing you know...he's got the infamous middle-aged gut. He could afford to lose about 25-30 pounds.

Let's also assume that Barry has a very tight schedule, so time is a factor. Barry feels he has to emphasize either restricting calories or increasing movement. If that's the case...then dieting is the better option. (Worth noting: The average American adult spends in excess of two hours surfing social media. So, in lieu of "doomscrolling" or engaging in useless internet flame wars, I think many people could spend time much more productively. Such as exercising.)

A recent scientific study highlighted the role that diet plays in weight loss versus the role that exercise plays. The study concluded that the primary culprit in obesity was processed food, and not the lack of movement. (2)

For the 4,213 adults in their study, the researchers used two different measures of obesity — BMI and body fat percentage, which is a much more accurate gauge of non-muscle weight. Participants came from 34 populations over six continents, and had a wide range of lifestyles and occupations.

The authors of the study wrote that the results "challenged the hypothesis that decreased physical activity contributes to rises in obesity ...instead, our results suggest that dietary intake plays a far greater role than reduced (exercise) expenditure."

The study clarified the results by stating that the nutrient composition of ultra-processed foods might encourage over-consumption. The most egregious offender in the "junk food" category is sugary drinks. The American Heart Association lists sweetened beverages as the single biggest contributor to sugar intake. (3)

One 12-ounce can of Coke contains 39 grams of sugar, which exceeds the AHA daily recommendation for both men (36 grams) and women (25 grams). If you're looking for a great way to reduce fat, quit drinking your calories.

In summary, if weight loss is the only goal for someone looking to lose 25-30 pounds — then go with restricting calories. But, as the famous London Bus Study demonstrated, the equation is very simple: move more if you want to live longer.

Sources and footnotes:

(1) L Grevendonk et. al (06/08/2021) "Impact of Aging and Exercise on Skeletal Muscle Mitochondrial Capacity, Energy Metabolism, and Physical Function." Nature Communications

(2) Amanda McGrosky, Amy Luke, Leonore Arab "Energy Expenditure and Obesity Across the Economic Spectrum." Proceedings of the Natural Academy of Science of the United States of America (PNAS)

(3) The American Heart Association "How Much Sugar is Too Much?" (09/23/2024)

Joshua Brandt is an Oakland based personal trainer. He can be reached at joshua@joshuabrandtpt.com or (415) 412-7339. 

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