They’ve cut down on calories and take regular exercise yet they’re still not losing weight. The only other possible diagnosis, they expertly conclude, is a slow metabolism.
What is a slow metabolism? How does it affect your weight, and can you do anything to speed it up?
Professor James Timmons, a metabolism expert from Loughborough University, gives your metabolism a closer examination.
What is metabolism?
Metabolism describes all the chemical processes that go on continuously inside the body to keep you alive and your organs functioning normally, such as breathing, repairing cells and digesting food.
These chemical processes require energy. The minimum amount of energy your body requires to carry out these chemical processes is called the basal metabolic rate (BMR).
Your BMR accounts for anything between 40% and 70% of your body’s daily energy requirements depending on your age and lifestyle. A ‘slow metabolism’ is more accurately described as a low BMR.
There are many calculators that work out your daily energy needs available online. Look out for calculators using the Harris-Benedict equation.
Do some people have a faster metabolism than others?
Body size, age, gender and genes all play a role in determining your metabolic rate.
Muscle cells require more energy to maintain than fat cells, so people with a higher muscle to fat ratio tend to have a higher BMR.
As we get older, we tend to gain fat and lose muscle. This explains why the BMR tends to decrease with age.
In general, men tend to have a faster metabolism as they have more muscle mass, heavier bones and less body fat than women, which is why their daily calorie allowance is higher.
Your metabolism may be partly determined by your genes, although this is not yet fully understood. Genes definitely play a role in muscle size and your ability to grow muscles, both of which affect your metabolism.
Am I fat because of a slow metabolism?
People who struggle to lose weight often blame a slow metabolism. However, numerous studies involving thousands of people worldwide have failed to find evidence to support the widely held belief that overweight people must have slower metabolic rates.
In fact, the opposite appears true: overweight people may actually have a higher metabolism than their leaner counterparts, reflecting the energy requirements of maintaining a larger body size. When you account for differences in body size and composition, there is a remarkable similarity in energy expenditure between individuals.
Research has also shown that people tend to eat more than they think they do. When asked to write down everything they've consumed in a day, many people tend to report eating far less than they actually do.
More often than not, the reason you’re putting on weight is not because of a slow metabolism, it’s because you’re eating and drinking more calories than you're burning. It may be hard to accept, but staying on top of the number of calories you eat is key to losing weight and keeping it off. Our 12-week weight loss plan will help you lose weight by tracking your calories.
Can losing weight too fast slow my metabolism?
Crash diets and other calorie-restricted diets can reduce your BMR. With some diets, your body is forced to break down muscle to use for energy. The lower your muscle mass, the slower your metabolism. With less muscle and a slower metabolism, it then becomes a lot easier to put body fat back on after coming off the diet.
What can I do to speed up my metabolism?
It is claimed that certain foods and drinks can boost your metabolism, including green tea, black coffee, spices and energy drinks. The evidence behind these claims is flimsy, the effect on your metabolism is marginal at best and each person will respond differently to each product.
While you don't have much control over the speed of your metabolism, you can control how many calories you burn through your level of physical activity. The more active you are, the more calories you burn. In fact, some people who are said to have a fast metabolism are probably just more active – and maybe more fidgety – than others.
Here are the three most effective ways of burning calories:
Aerobic exercise is the most efficient way to burn calories. You should aim to do 150 minutes of aerobic activity, such as walking, cycling and swimming, a week. You can achieve this target by doing 30 minutes five days a week and breaking down your activity sessions in chunks of 10 minutes. To lose weight, you are likely to need to do more than 150 minutes a week and make changes to your diet. Physical activity guidelines for adults.
Muscle tissue burns more calories than fat tissue, so increasing your muscle mass will help you lose weight. Don't worry, you don't need to turn into Arnold Schwarzenegger! Aim to do muscle-strengthening activities on two or more days a week that work all major muscle groups (legs, hips, back, abdomen, chest, shoulders and arms). Examples of muscle-strengthening activities include lifting weights and high intensity bouts of exercise. Heavy gardening may also do the job.
Being constantly on the move and Get ideas on fitting more activity into your day.
Can certain medical conditions cause a slow metabolism?
Some diseases and conditions can slow a person’s metabolism, such as Cushing’s syndrome and hypothyroidism (an underactive thyroid), but more often than not, people’s weight is a matter of consuming more calories than they burn. However, if you feel that you may have a problem that’s not responding to lifestyle changes, seek medical advice. Read Nine medical reasons for putting on weight.