When the body burns energy, it draws on stored fat through a process called lipolysis. Hormonal signals, primarily from adrenaline and noradrenaline, bind to receptors on fat cells and trigger the release of stored fatty acids into the bloodstream to be used as fuel. This process happens throughout the body, but not uniformly.

Fat cells in different regions of the body have different receptor profiles. Alpha-2 adrenergic receptors suppress lipolysis when activated. Beta-2 adrenergic receptors stimulate it. Areas that are commonly described as stubborn — the lower abdomen, inner thighs, flanks, and submental region — tend to have a higher density of alpha-2 receptors.

This means that even when adrenaline is elevated through exercise, the fat cells in these zones are biologically less responsive to the lipolytic signal. Blood flow to these areas is also often lower, further reducing the delivery of the hormonal signals needed to initiate fat release.

Hormones influence where the body stores fat and how readily it releases it. Oestrogen plays a significant role in directing fat toward the hips, thighs, and lower body in women. Cortisol drives fat accumulation in the abdominal region. Insulin resistance concentrates adipose tissue centrally.

This is why two people following the same diet and exercise plan can have very different distributions of body fat and very different experiences of where fat loss occurs and where it does not.

Dietary and exercise interventions reduce overall body fat. They do not selectively target specific resistant deposits. Non-surgical body contouring treatments, by contrast, work directly on the fat cells in a targeted area. Lipolytic injections use compounds to disrupt the fat cell membrane, permanently destroying a portion of the fat cells in the treated zone. HIFU and contouring technologies address fat and skin laxity simultaneously.

These treatments are not alternatives to a healthy lifestyle. They are tools for addressing the structural component of body fat distribution that lifestyle changes cannot reach.