Not all pounds you gain carry the same weight.

Being overweight or obese can contribute to a host of health problems, like chronic diseases, heart attacks and even premature death — especially in older age.

But according to new research, the age at which you start tipping the scales can have a real impact on your life expectancy.

Obesity is rising across age groups. Among people under 25, the number of obese and overweight people increased from 198 million to 493 million between 1990 and 2021 — and is expected to reach 746 million by 2050 without significant intervention.

While the scale naturally creeps up as we get older, a large study from Sweden found that weight gained before age 30 is more strongly linked to early death than weight gained in middle or later adulthood.

The study tracked more than 620,000 people over several decades, measuring their weight at least three times between ages 17 and 60.

While the average amount of weight gained over the course of the study was around 40 pounds, the rate wasn’t steady and was fastest in young adulthood, especially for men.

People who became obese before age 30 faced a roughly 70% higher risk of premature death than those who didn’t become obese by age 60.

Rapid weight gain between ages 17 and 29 was linked to increased death rates from a wide range of health conditions, including heart disease, Type 2 diabetes, kidney disease and certain cancers.

Type 2 diabetes showed the strongest connection between cause of death and early obesity.

High blood pressure and liver cancer in men and uterine cancer in women also had strong ties to steep weight gain in youth.

And within this same age range, for every additional pound gained per year, men faced an 18% higher risk of death from any cause, while women had a 16% higher risk.

Meanwhile, weight gain later in life or after age 30 was associated with higher death rates, but the risk lessened the later the weight came on.

The findings suggest that the longer someone lives with obesity, the more dangerous it becomes over time.

For women, however, weight gain at any age, especially between 45 and 60, was linked to higher rates of death from cancer.

In men, the link between weight gain and cancer death followed the same pattern, in which gaining weight early in life made the most impact.

The study’s consistent findings that weight gain early in life had strong connections to early death from various causes “support the importance of early and sustained obesity prevention strategies to reduce premature mortality,” the study authors wrote.