Yes, feet can get bigger when weight is gained, often requiring a larger shoe size. This size increase is not due to changes in bone structure, but rather a combination of mechanical pressure and soft tissue changes. The feet are the foundation that supports the entire body, absorbing significant force, up to 120% of body weight when standing. Increased body mass subjects the feet to greater stress, causing measurable changes in their shape and volume. The resulting increase typically manifests as a wider and sometimes longer foot, clarifying why shoe sizes shift with weight gain.
How Increased Body Load Affects the Foot Structure
The primary mechanical factor in foot size increase is the effect of sustained pressure on the longitudinal arch. This arch acts as a spring and shock absorber, supported by ligaments and the plantar fascia. When body mass increases, the downward force on the feet rises significantly, overloading these supporting structures.
This prolonged pressure causes the ligaments and plantar fascia to stretch out over time. As the arch loses tension and flattens, the foot pronates, rolling inward and spreading out. This mechanical flattening, or arch collapse, increases both the length and the width of the foot.
The Contribution of Adipose Tissue
A second reason for a larger foot size is the deposition of fat tissue within the foot itself. The body stores excess energy as adipose tissue throughout the body, including the feet. This localized fat accumulation increases the overall volume and thickness of the foot, independent of arch collapse.
Increased body mass is also linked to greater fluid retention and inflammation, contributing to swelling in the lower extremities. This condition, known as edema, makes the feet appear larger and puffier. The combination of fat deposits and fluid retention creates a bulkier foot that requires more space inside a shoe.
Are Foot Size Changes Permanent
The reversibility of foot size change depends on which of the two mechanisms caused the increase. When weight is lost, the reduction in body fat volume causes adipose tissue in the feet to decrease, and fluid retention subsides. This reduction in soft tissue bulk can lead to the foot becoming narrower and less thick, sometimes resulting in a decrease of up to a full shoe size.
However, structural changes related to arch collapse are often less reversible. If the ligaments and tendons supporting the arch have been significantly overstretched, they may not fully retract to their original tension. This sustained flattening means the foot may remain longer and wider than its original size, even after weight loss. A permanent adjustment to a larger length or width size may still be necessary.