Excessive Weight Bearing Compromises Foot Structure and Function Across the Lifespan - The Mechanobiology of Obesity and Related Diseases - page 166

Relevant to this review was that the most common pain location was the legs and feet
(44.8 %; grouped together), followed by the back (39.8 %) and the neck and
shoulders (31.2 %). Compared to the non-obese individuals, the obese participants
were twice as likely, and severely obese participants were more than four times
as likely, to have chronic pain, even after adjusting for other risk factors [ 128 ].
Individuals in higher BMI categories also reported more frequent and more severe
pain than their counterparts with lower BMI values. The authors speculated the
association between chronic pain and obesity was likely in part, due to the greater
mechanical loading of weight-bearing structures because of excess body mass,
together with an increase in inflammatory markers associated with obesity (as
described in Sect. 4.3.2 ). In a more recent investigation, Mickle and Steele
(unpublished) reported almost two-thirds of older obese participants reported suf-
fering from foot pain, with 40 % of the obese older adults classified as having
disabling foot pain. The severity of foot pain was reflected in Short Form (36) Health
Survey scores, whereby, compared to their learner counterparts, the older obese
participants had a significantly lower total score, with the physical health dimension
being the domain that was limiting their health-related quality of life. The same older
obese individuals also exhibited functional impairment during simple weight-
bearing activities of daily living, such as walking (Mickle and Steele, unpublished).
The alterations to foot structure and foot function and the increased foot pain
found in older obese individuals are likely to contribute to the overall lower
extremity impairment that has been reported to affect obese older people [ 119 ].
Consistent with previous research [ 109 ], older obese adults have been shown to
exhibit functional impairment during the simple daily activity of walking; walking
with a reduced speed, a smaller stride and step length, and a wider step width, than
their leaner counterparts (Mickle and Steele, unpublished). Older obese partici-
pants have also been shown to display weaker toe flexor muscles than both their
overweight and non-overweight counterparts, although there were no significant
differences in ankle dorsiflexor strength among the three participant groups
(Mickle and Steele, unpublished). Currently, we do not know whether foot muscle
strength has been compromised in the obese participants due to physical inactivity
and/or atrophy due to fatty infiltration of the muscles [ 132 ], although this warrants
further investigation.
Interestingly, research has shown that reducing excess body mass can alleviate
some of the foot-related symptoms associated with obesity in older adults. For
example, substantial weight loss (average 41 ± 15 kg) following gastric bypass
surgery resulted in an 83 % improvement in foot complaints [ 133 ]. Similarly,
McGoey et al. [ 134 ] found the proportion of morbidly obese people suffering from
foot pain was reduced from 21 to 1 % following weight loss surgery. Therefore,
interventions designed to reduce excess body mass, particularly excess fat mass, in
obese older adults are recommended to improve foot pain, functionality and quality
of life for these vulnerable individuals. However, if foot pain is inhibiting mobility,
non-weight bearing activities should be encouraged to aid with weight loss.