The conventional wisdom is that after 30, we get what is called the middle age spread. We gain weight, exercise tends to become pointless, and we conveniently blame it on our slowing metabolism, isn't it?

Along with this, we think that women tend to put on weight easier than men due to slower metabolism.

Added to that are things like menopause and menstrual cycle which are believed to make things worse.

The study is all about what age does to our metabolism. Can we blame age for our expanding waistline? Is there a gender bias in our understanding of metabolism? Let's break it down.

Metabolism is how many calories you burn through a day. It is the process by which your body converts what you eat and drink into energy

Researchers analyzed calories used up by more than 6,600 people aged between one week and 95 years old across 29 countries as they went about their daily lives.

More than 80 researchers from different labs contributed to the report.

They used what is known as the isotope water technique or the doubly labeled water method.

By calculating how much hydrogen and oxygen you lose per day, you can calculate how much carbon dioxide the body produces every day.

That's how you measure calories burned daily.

With this, the scientists were able to measure the total daily energy expenditure, not just the essential calories required to stay alive, which other studies have focused on so far.

Until age 1, calorie burning is at its peak. A 1-year-old burns calories 50 percent faster for their body size than an adult.

Then, our metabolisms seem to gradually slow down by about 3 percent a year until 20. There's no real spurt over puberty.

After 60, researchers found that our metabolisms seem to slow down by about 0.7 percent a year.

But a person in their 90s needs 26 percent fewer calories each day than someone in midlife.

The study busted some important gender stereotypes too.

Puberty, menopause - both had no effect. Even during pregnancy, a woman’s calorie needs were no more or less than expected, given the added weight of a growing baby.

If you're gaining weight in your middle age, maybe you cannot blame metabolism anymore!

Metabolism changes with age, but just not as we thought it would. And teens are not big calorie burners.

The study shows the importance of nutrition in infants to grow up to be healthy adults. But more research is needed to better understand the high metabolism of babies.

It's also surprising that the metabolism changes are similar in men and women. We think gender and hormones affect metabolism, but the study also turns that on its head.

Another way that the findings could be useful is in tailoring health treatments to specific people and specific age ranges.

Regardless of the new data, regular physical activity, maintaining muscle mass and nutritious diet is the way to go.