Flanks and belly that resist diet and exercise: why

You have lost weight, your arms and face have slimmed down, your trousers fit better. But the belly, or those “love handles” on the flanks, are still there. It is one of the most common complaints in body aesthetics consultations, and it has biological explanations: not all fat is the same, and the body does not lose it equally in every area.

But before talking about aesthetics, there is a distinction that matters for health: the fat that can be pinched beneath the skin is not the same as the fat that accumulates around the organs. And, sometimes, the “belly” is not even fat.

Two types of belly fat

Subcutaneous fat

It sits under the skin, above the abdominal muscles. It is the one that can be pinched and the one that forms the “love handles” on the flanks and the “soft” belly. From a health point of view, it is relatively benign. It is mainly an aesthetic matter.

Visceral fat

It sits inside the abdomen, beneath the muscles, around the liver, intestines and other organs. It cannot be pinched. It makes the belly firm and protruding, sometimes in a body that does not appear to carry much excess weight. It is metabolically very active (Jensen, 2008) and is associated with:

• Insulin resistance and type 2 diabetes.
• Hypertension and cardiovascular disease.
• Fatty liver.
• Chronic low-grade inflammation.

Men tend to accumulate more visceral fat; women, more subcutaneous fat on the hips and thighs, until the menopause, when the distribution changes and abdominal fat increases.

Waist circumference

It is the simplest way to estimate abdominal fat and the associated risk. It is measured with a tape measure, standing, halfway between the last rib and the top of the hip bone, at the end of a normal exhalation.

Reference values for European populations; they may be different in other ethnic groups (WHO, 2008).

Another useful measure is the waist-to-height ratio: a value above 0.5 (waist greater than half your height) also suggests excess abdominal fat.

If your waist circumference is above these values, speak to your family doctor. Before being an aesthetic matter, it may be a health matter, and contouring treatments do not reduce visceral fat.

Why some areas resist more

Fat cells are not all the same

To use stored fat, the body needs to “unlock” it (lipolysis). This process is controlled mainly by catecholamines (adrenaline and noradrenaline), which act on two types of receptors in the fat cells:

• Beta receptors: stimulate the release of fat.
• Alpha-2 receptors: block that release.

The proportion between the two varies from area to area. Classic physiology studies (Wahrenberg et al., 1989) showed that the subcutaneous fat of the lower body (hips, thighs, buttocks) in women has more alpha-2 activity and responds less well to mobilisation signals. In men, abdominal subcutaneous fat tends to behave similarly. Visceral fat, by contrast, is more “responsive” and tends to decrease earlier with diet and exercise, which is good news for health, even when the mirror shows no great change.

Genetics and sex

The way each person distributes fat is, to a large extent, inherited. There are families in which fat accumulates on the belly and families in which it accumulates on the hips. The order in which the body loses fat when slimming also varies, and the last areas to change are often the same ones that were the first to accumulate.

Hormones and age

• Menopause: the fall in oestrogens shifts fat to the abdomen, including visceral fat. Many women notice their belly growing without changes in weight. See Localised fat in the menopause: why the body changes and what helps.
• Low testosterone in men: associated with more abdominal fat.
• Cortisol: chronic stress and some diseases or medicines (such as corticosteroids at high, prolonged doses) favour abdominal accumulation.
• Age: with the loss of muscle mass, energy expenditure decreases and fat tends to accumulate in the trunk.

Lifestyle

• Short or poor-quality sleep is associated with more abdominal fat and greater appetite.
• Alcohol contributes calories and is associated with greater abdominal accumulation.
• Prolonged sedentary behaviour, even in those who exercise a few times a week.

The myth of “spot reduction”

Doing sit-ups does not burn belly fat. In one study (Vispute et al., 2011), six weeks of abdominal exercise without other changes did not reduce abdominal fat, although they improved muscle strength. The body draws energy from its stores globally. This topic has a dedicated article: Spot fat reduction: myth or reality.

When the belly is not (only) fat

Abdominal diastasis

It is the separation of the two sides of the rectus abdominis muscle (the “abs”) at the midline, which becomes wider and weaker. It is very common in pregnancy and can persist: in a Norwegian study (Sperstad et al., 2016), around a third of women still had diastasis a year after giving birth. It can also occur in men, especially with abdominal obesity or repeated straining.

Signs: a protruding belly that does not improve with weight loss, a “ridge” or “valley” at the midline when you lift your head lying on your back, sometimes lower back pain.

A simple test: lying on your back, knees bent, lift your head and shoulders slightly. With your fingers, feel the midline above and below the navel. If the fingers sink between the muscles over a width of two or more fingers, speak to your doctor or a specialist physiotherapist. Treatment involves targeted exercise and, in selected cases, surgery. Fat-reduction treatments do not correct diastasis.

Abdominal bloating

A belly that varies greatly through the day, is flat in the morning and protruding in the evening, or that swells after certain meals, is probably bloating (gas, constipation, intolerances, irritable bowel syndrome), and not fat.

If you ticked any, the swelling deserves medical assessment.

Excess skin

After pregnancies or major weight loss, the “belly” may be mainly skin and not fat. Fat treatments do not resolve it and can worsen laxity.

Posture

A forward tilt of the pelvis (hyperlordosis) pushes the belly out and accentuates the flanks. Strengthening the core and correcting posture changes the appearance, without changing the fat.

What really works

• Overall fat loss. A moderate, sustained calorie deficit is the foundation. The belly and flanks may be among the last areas to change, but they do change.
• Regular aerobic exercise. Meta-analyses (Vissers et al., 2013) show that it reduces visceral fat, even with little weight loss. It is the type of fat that matters most for health.
• Strength training. It preserves and increases muscle mass, improves metabolism and body composition and, together with the core, improves posture and contour.
• Sufficient protein and minimally processed food, which help with satiety and with preserving muscle.
• Sleeping 7 to 9 hours.
• Cutting back on alcohol.
• Managing stress, as far as possible.
• Patience and the right measures. Use waist circumference and photographs, not just the scales. Visceral fat loss may happen before it is noticeable in the mirror.

If, despite this, there is significant excess weight, the doctor may assess other options, including pharmacological or surgical treatment of obesity.

Body contouring treatments: what they can and cannot do

For those close to their healthy weight who have localised subcutaneous fat deposits that do not respond, there are body contouring treatments. It is important to understand what they do.

Sources: Ingargiola et al., 2015; StatPearls (paradoxical adipose hyperplasia).

Limits worth knowing

• They act only on subcutaneous fat. They do not reduce visceral fat or cardiovascular risk.
• They are not a slimming treatment. The best candidates are close to their healthy weight, with localised deposits that can be pinched.
• They do not correct diastasis or excess skin. On loose skin, reducing fat may make the appearance worse.
• Results depend on lifestyle. The cells that are eliminated do not come back, but the remaining ones can grow with weight gain.
• They require a prior assessment. Some conditions rule out certain treatments (for example, cold-related conditions, in cryolipolysis; pregnancy; hernias in the area).

This article is for information purposes and does not replace a consultation. The results of any treatment vary from person to person.

Frequently asked questions