Mass moves mass is often cited for why morbidly obese people can lift very heavy loads with little training.
So why are some big people not that strong in the absolute sense?
I was inspired to cover this topic after reading numerous Reddit threads about a morbidly obese woman who posts videos on Instagram and TikTok of herself performing hex bar lifts, deadlifts and some “strongman” moves despite apparently having very little training.
Some Reddit posters estimate her weight at 500 pounds; some more; some less.
I’d say she’s around 420 – at 5’9 – though in the past she’s visibly weighed more.
“Mass moves mass” has come up quite a bit when discussing her very heavy lifts.
Another way to put this is “weight moves weight.”
However, this isn’t always true. When I was a personal trainer, I had several morbidly obese clients who absolutely would not have been able to perform a 400 pound trap bar lift, as did the influencer mentioned above.
For a woman, a 400 pound hex bar lift is seriously heavy, which is why you could be working out at different gyms for many years and never see a woman do this.
If we take a look at the morbidly obese people at Walmart – known as “Walmart fat,” it’s just not believable that they could just up and deadlift a 225 pound barbell with no training.
In fact, even if we put a few months of training under their belt, I just can’t picture someone who’s Walmart fat being able to pull 225, let alone 305.
Well…I suppose some of the younger women I see there could possibly do this after a few months of strict training – and these are the morbidly obese women who naturally appear to have more muscle mass than the average woman their size.
Reasons Why Mass Doesn’t Always Move Mass
I’ve seen big women bench pressing small amounts of weight, such as 65, 75 and 85 pounds.
One might argue that they could actually lift significantly more but are holding back due to an unrealistic fear that lifting any more will add bulk to an already very big body.
And in fact, I’ve had clients who’d been holding back for this very reason.
However, I’ve seen morbidly obese women struggling to complete a set with a light barbell.
Those last few reps at even 75 pounds cause visible strain in them. “Mass moves mass” doesn’t apply here. And these are young women, too.
One might also point out that maybe if they used more weight, their shoulders will hurt because they haven’t been training long enough to acclimate tendons to high resistance.
I’ve always instructed my clients to build up tendon strength first, because muscles gain strength faster than do tendons. Let the rotator cuff tendons catch up.
But I doubt that these women are thinking along these lines when using no more than an 85 pound barbell.
Based on what my eyes have observed, they’re lifting under a hundred because they simply can’t do a set with more weight.
What about the deadlift and back squat? What about strongman moves?
Absolute Strength vs. Strength Relative to Body Mass
De J. Tomlinson (2016), in Current Opinion in Clinical Nutrition and Metabolic Care, reviewed the effects of obesity on skeletal muscle strength.
He reported that “obese individuals, regardless of age, have a greater absolute maximum muscle strength compared to non-obese persons.”
The extra weight acts as a chronic overload stimulus — especially for antigravity muscles like those in the legs.
Every single one of my morbidly obese clients were able to leg press far more weight than their thinner counterparts.
But the Tomlinson research also points out that from a relative standpoint – comparing weight lifted to weight of the lifter’s body — “obese individuals appear weaker.”
For instance, reduced mobility in the legs could impact the squat. Midsection girth could interfere with an efficient deadlift.
Maffiuletti et al (2013) in Obesity Reviews similarly concluded that although very fat people display higher absolute muscle strength versus lean counterparts, they show lower strength per unit body mass — but maintain comparable strength per unit of fat-free mass or muscle size.
They suggested that intrinsic muscle quality isn’t impaired; rather, excess fat mass and impaired motor coordination may explain reduced functional performance.
An example of where this is obvious would be a weighted walking lunge and the Smith machine split squat.
Why Physics Isn’t the Whole Story
The phrase “mass moves mass” reflects the basic principle that greater mass often implies greater capacity to generate force.
This is easy to visualize with certain exercises such as the leg press, sled push and deadlift.
A heavy body is forced to chronically bear all those extra pounds.
This is going to show in some gym moves, especially if the person is younger and not yet severely impacted by obesity related arthritis.
But there are additional reasons why not all morbidly fat people can hoist around impressive absolute loads.
Years of significant overweight can warp their body, leading to an off-kilter gait or waddle, and/or odd compensatory positions or movements when under physical stress.
These warps can limit how much weight they can lift, especially in movements that demand more complexity in form such as a split barbell squat, the back squat and a tire flip.
Simpler moves, such as the bench press, leg press and weighted carries, are friendlier to a body whose massive size has warped it.
Cheryl Haworth is 5’9 and weighed nearly 300 pounds while competing as an Olympic style lifter in the 2000, 2004 and 2008 Oympics. She’s exceptionally large for even this style of lifting.
Cheryl Haworth. NOTE: Her body proportions are extremely advantageous for this sport.
Fat distribution is another factor. Two 300 pound women can have completely different-looking bodies.
The pear shape has more of an advantage in the deadlift and squat; there’s not as much middle to “get in the way.”
Further, the excessive mass below their center of gravity acts as a solid base of support for these compound movements.
Someone with disproportionate fat in the middle (apple shape) would struggle more with the deadlift and squat.
They’ll have a nice little advantage in the bench press: shortened range of motion due to midsection girth.
Chronic morbid obesity in some people can also leave them feeling chronically fatigued.
Persistent joint aches can also be present, along with a bad back.
These factors, plus the others mentioned here, are why “mass moves mass” doesn’t apply to every single morbidly obese man or woman.
Lorra Garrick is a former personal trainer certified by the American Council on Exercise. At Bally Total Fitness, where she was also a group fitness instructor, she trained clients of all ages and abilities for fat loss and maintaining it, muscle and strength building, fitness, and improved cardiovascular and overall health.
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