Weight-loss goals: why losing 5–10% of body weight can improve health

If you are among the one in three people whose New Year’s resolution was to lose weight, you may now be wondering what weight-loss target you should realistically aim for.

Yet searching online for "setting a weight loss goal" is likely to leave you with more uncertainty rather than clear answers.

The vast number of weight-loss apps and calculators can make choosing a target appear straightforward. Most use a body mass index (BMI) calculator to identify a "healthy" weight, then suggest a goal weight within that range.

Your feed may then be packed with slim influencers promoting diets that supposedly help you shed ten kilograms in a month, alongside adverts for diets, tablets and exercise programmes that claim you can lose weight quickly and effortlessly.

Many of these sales messages imply that substantial weight loss is essential for good health, making the task seem unattainable. However, evidence shows that significant health improvements do not require you to lose a huge amount of weight.

Why BMI is a flawed weight-loss goal measure

We live in a society that is preoccupied with numbers, so it is unsurprising that we rely on measurements and formulae to assess weight. The most widely used is BMI, which compares body weight with height.

BMI places people into underweight, normal (healthy) weight, overweight or obese categories, and it can be a useful screening tool for weight and health.

However, it should not be the sole indicator of a healthy weight when setting weight-loss goals because it:

• does not take account of two important factors connecting body weight and health: body-fat percentage and where fat is distributed
• fails to reflect substantial differences in body composition related to gender, ethnicity and age.

How weight loss can improve health

Losing only 5–10% of body weight - 6 to 12 kg for a person weighing 120 kg - can bring meaningful health benefits in four main areas.

1. Lowering cholesterol

Obesity raises the likelihood of having excessive low-density lipoprotein (LDL) cholesterol, commonly called bad cholesterol. This happens because carrying extra weight alters the way the body produces and handles lipoproteins and triglycerides, another fat molecule used for energy.

High levels of bad cholesterol and triglycerides are harmful because they can narrow the arteries and restrict blood flow. This raises the likelihood of heart disease, heart attack and stroke.

However, research indicates that losing only 5% of body weight can improve total cholesterol, LDL cholesterol and triglyceride levels.

2. Bringing down blood pressure

Blood pressure is classed as high when readings exceed 140/90 on at least two separate occasions.

Extra body weight is associated with high blood pressure through several mechanisms, including effects on how the sympathetic nervous system, blood vessels and hormones control blood pressure.

Put simply, high blood pressure means the heart and blood vessels must work harder and operate less effectively. Over time, this damages the arteries and increases the risk of heart disease, heart attack and stroke.

As with cholesterol, a 5% reduction in body weight improves both systolic blood pressure - the first figure in a reading - and diastolic blood pressure - the second figure.

A meta-analysis of 25 trials examining the effect of weight reduction on blood pressure also showed that every kilogram lost improved blood pressure by one point.

3. Cutting the risk of type 2 diabetes

Excess body weight is the leading modifiable risk factor for type 2 diabetes, particularly for people who carry substantial visceral fat around their abdomen (belly fat).

This additional weight can prompt fat cells to release pro-inflammatory chemicals, interfering with the way the body controls and uses insulin made by the pancreas. This can result in high blood sugar levels.

Without careful management, type 2 diabetes can cause serious medical problems, including damage to the heart, blood vessels, major organs, eyes and nervous system.

Research suggests that a 7% weight loss lowers the risk of developing type 2 diabetes by 58%.

4. Easing joint pain and osteoarthritis risk

Having excess weight can inflame and damage the joints, leaving people more vulnerable to osteoarthritis.

Observational research indicates that being overweight doubles a person’s likelihood of developing osteoarthritis, while obesity makes the risk four times greater.

Even modest weight loss reduces this strain on the joints. One study found that every kilogram lost produced a fourfold reduction in the load placed on the knee with every step during everyday activities.

Build habits that work long term

If you have attempted to lose weight only to find the kilograms return nearly as fast as they disappeared, you are far from alone.

An analysis of 29 long-term weight-loss studies found that participants regained over half the weight they had lost within two years. By five years, they had regained more than 80%.

Weight loss moves the body outside its comfort zone and activates a survival response. In turn, the body resists the loss by setting off several physiological processes intended to protect body weight and "survive" starvation.

Just as this challenge has evolutionary roots, so does the answer. Long-term weight loss success depends on:

• losing weight in small, manageable amounts that can be maintained - specifically, periods of weight loss followed by periods of weight maintenance, repeated until you reach your goal weight
• introducing lifestyle adjustments gradually, so you build habits that can last for life.

Setting a goal of reaching a healthy weight may feel overwhelming. However, it does not need to be a fixed number determined by a "healthy" BMI range. Losing 5–10% of body weight can deliver immediate health benefits.

At the Boden Group, Charles Perkins Centre, we are studying the science of obesity and running clinical trials for weight loss. You can register here to express your interest.

Nick Fuller, Charles Perkins Centre Research Program Leader, University of Sydney

This article is republished from The Conversation under a Creative Commons license. Read the original article.