What Determines Speed of Weight Loss?


There are a number of factors which affect weight loss and the speed with which a person loses weight. This article outlines the main issues which can have an effect on this. Some of them are not things which can necessarily be changed.


Your fat-to-muscle ratio greatly affects your ability to lose weight. Because women typically have a greater fat-to-muscle ratio than men, they have a 5-10% lower resting metabolic rate (RMR) than men of the same height. RMR is the number of kilojoules your body needs to maintain normal bodily functions, such as breathing and pumping blood.

This means that women generally burn 5-10% fewer calories than men at rest. Thus, men tend to lose weight quicker than women following a diet equal in calories.


One of the many bodily changes that occur with aging is alterations in body composition - fat mass increases and muscle mass decreases. This change, along with other factors like the declining calorie needs of your major organs, contributes to a lower RMR.

In fact, adults over age 70 can have RMRs that are 20-25% lower than those of younger adults. This decrease in RMR can make weight loss increasingly difficult with age.

So it's important, as you get older, to keep a good level of protein intake and to partake in some exercise to maintain a good level of lean muscle mass.

Starting Point

Your initial body mass and composition may also affect how quickly you can expect to lose weight.

A person weighing 100 kgs that loses 3 kgs has lost 3% of their body weight, but a person weighing 60 kgs that loses 3 kgs has lost 5% of their body weight. A person weighing more will generally lose kilograms more quickly, simply because of the higher starting point.


Sleep tends to be an overlooked yet crucial component of weight loss. Chronic sleep loss can significantly hinder weight loss and the speed at which you shed weight. Just one night of sleep deprivation has been shown to increase your desire for high-calorie, nutrient-poor foods, such as cookies, cakes, sugary beverages, and chips.

One 2-week study randomized participants on a calorie-restricted diet to sleep either 5.5 or 8.5 hours each night. Those who slept 5.5 hours lost 55% less body fat and 60% more lean body mass than those who slept 8.5 hours per night.


Many medications, such as antidepressants and other antipsychotics, can promote weight gain or hinder weight loss.

Medical Conditions

Illnesses, including depression and hypothyroidism, a condition in which your thyroid gland produces too few metabolism-regulating hormones, can slow weight loss and encourage weight gain.

Family History

There is a well-established genetic component associated with people who have overweight or obesity, and it may affect weight loss. Whether this is genetic or merely due to following familiar family eating patterns is uncertain.

Yo-Yo Dieting

This pattern of losing and regaining weight can make weight loss increasingly difficult with each attempt, due to a decrease in resting metabolic rate.


Age, gender, and sleep are just a few of the many factors that affect weight loss. Others include some medical conditions, family history, and the use of certain medications. While some of these factors cannot be changed, at least an understanding of their effect on speed of weight loss can help to manage expectations.