As we reach our 30's, our bodies usually need less energy, meaning we may not be able to eat the way we did in our 20's. Then, as you move past 40 and head to middle age, changes in muscle, hormones and metabolism all make it harder to stay trim. But it's not a lost cause.
Although the prevalence of obesity increases with age, weight gain is actually greatest across the younger years of adult life — late twenties and thirties — and diminishes gradually over time as adults get older, says Tucker.
There are a number of key factors at play, DeLauer explains. Firstly, your hormones. "You start gaining weight when your testosterone levels decline, which is a very common thing," he says. Secondly, the body's insulin resistance changes over time: "Our inability to deal with glucose increases with age," he says.
The finding of the study suggests that people in middle age certainly gain weight and it is harder for them to lose it, but slow metabolism is not the real reason behind it. It was revealed that from the 20s to the 50s the energy expenditure is the most stable.
One of the main reasons that undereating can lead to weight gain is because consuming too few calories can cause your resting metabolic rate to slow down. This means you may burn fewer calories throughout the day.
Low thyroid: Your thyroid is a major regulator of your metabolism and other key hormones. If your thyroid hormone is low, it can slow your metabolism, resulting in weight gain. Low testosterone: Testosterone is usually only associated with men, but women have it too and it plays a role in weight and metabolism.
If you have a slow metabolism, your genes may be to blame. Or you may not have enough lean muscle mass. People with lean, muscular bodies burn more calories than people with a higher percentage of body fat.
Your body is designed to hold onto as much fat as possible to store for times when food may be scarce. That makes losing weight difficult for most people. Factors at play include genetics, age, race and ethnicity, diet, physical activity, hormones, and social factors.
Genetics
Certain factors that could contribute to your difficulty losing weight are beyond your control. Research has shown that there is a strong genetic component to obesity. Twin studies have shown that between 60% to 90% of your predisposition to obesity could be genetic¹⁴.
For years, the assumption has been that your metabolism is slowing as you age. But a study that included 6,500 people from 29 countries shows that metabolism for both men and women really doesn't significantly drop off until you reach the age of 60.
Weight loss can be different for men and women. Men tend to gain weight until age 55, and then slowly start to lose it in the years that follow. This could be because men produce less testosterone after this age. Women, on the other hand, usually stop gaining weight once they hit age 65.
Muscle Mass
A month or two after you start exercising, your body composition may begin to change. You will likely gain muscle mass and may begin to lose some fat mass. Muscle weighs more than fat, but it also burns more calories.
A slow metabolism has many symptoms, and you're likely to have one if you find it difficult to lose weight and easy to gain weight. Other symptoms include fatigue, poor digestion, constipation, low mood, and a colder than average body temperature. All of these are caused by the lower production of energy and heat.
Regular exercise increases muscle mass and teaches the body to burn kilojoules at a faster rate, even when at rest. Drugs – like caffeine or nicotine, can increase the BMR. Dietary deficiencies – for example, a diet low in iodine reduces thyroid function and slows the metabolism.