Marked Weight Gain in Adulthood Increases Cancer Risk

Liam Davenport

November 09, 2016

LIVERPOOL, UK — Individuals who gain a substantial amount of weight during adulthood and move into another body mass index (BMI) category have a markedly increased risk for obesity-related cancers, the results of a large analysis indicate.

Men who moved from being normal weight to being overweight during adulthood had a 50% increased risk of developing obesity-related cancers compared with men who only gained steadily and stayed at a healthy weight.

Among women, an increase in BMI from normal weight to being obese during adulthood was associated with a 17% increased risk for obesity-related cancers compared with women who stayed at a healthy weight.

"This research shows how important it is to look at weight gain over a person's lifetime to give a clearer picture of cancer risk through life compared to assessing someone's BMI at a single point," commented lead researcher Hannah Lennon, PhD, research associate at the University of Manchester and the Health Research Center, United Kingdom.

Dr Lennon presented the findings here at the National Cancer Research Institute (NCRI) Cancer Conference 2016.

"This study provides a deeper understanding of the health implications caused by the obesity epidemic," commented NCRI director Karen Kennedy. "It helps paint the picture of how risk could accumulate over time for different people and could provide health professionals with a means to asses an individual's risk."

Study Details

For the current analysis, the researchers examined data on approximately 300,000 individuals from a US cohort that included approximately 117,500 men and 111,500 women for whom four BMI measurements were available.

The team set out to look for changes in BMI occurring from the ages of 18 to 65 years. They used latent class longitudinal models to cluster BMI trajectories over time, from which five sex-specific trajectories could be defined.

In men, the trajectories seen were as follows:

  • lean, moderate increase (68.1%)

  • lean, marked increase (4.8%);

  • medium, marked increase (31.7%); and

  • heavy increase (3.4%)

In women, the trajectories were as follows:

  • lean, stable (32.6%)

  • lean, moderate increase (41.1%)

  • lean, marked increase (21.1%)

  • heavy increase (3.5%)

Follow-up data covering a period that averaged 15 years was then used to determine the risk of developing obesity-related cancers.

The researchers note that the majority of the male study population fell into the lean to moderate-increase group (68%), which they used as a reference. Compared to this group, there was a significant increase in the lifetime odds ratio (OR) of developing obesity-related cancers (hazard ratio [HR] = 1.24) in the group that showed a medium marked increase in BMI. Even higher increases in cancer risk were seen in the lean to marked-increase group (HR = 1.50) and the heavy-increase group (HR = 1.53).

Only about a third of the women in this study fell into the lean, stable group (33%), which was used as a reference. Compared to this group, the lifetime ORs of developing obesity-related cancers for all the other groups were elevated. For women in the lean, moderate-increase group, HR = 1.07; for women in the lean, marked-increase group, HR = 1.17; and for women in the heavy-increase group, HR = 1.16.

There was no significant association between nonobesity-related cancers and BMI trajectory.

More Tailored Public Message?

Discussing the rationale for examining the association between BMI trajectory, as opposed to a single measure, and cancer risk, Dr Lennon told Medscape Medical News that it is known that "many cancers take years or decades to develop.

"We are very aware that there is a strong positive association for obesity and obesity-related cancers, but this relationship has been established by looking at an individual's BMI at one single time point," she commented.

Dr Lennon pointed out that for smoking, there is a strong, positive association between the risk of developing a cancer and both the length of time an individual smokes and how much they smoke.

She said: "We were trying to argue that your BMI at a single point gives us some kind of measure of how exposed you are to obesity, but we're more interested in how you've got to your BMI."

In other words, the aim was to identify people who had been relatively lean for their whole life and then rapidly put on weight, as opposed to people who had gained weight at a steady pace. "We're trying to quantify this lifetime BMI path, rather than the BMI at one single time point, which is the novelty in this work," she said.

The researchers are hoping that the findings can be used to develop more tailored public health messages and "precision treatment" for individuals.

Dr Lennon said: "We're hoping, by doing this piece of research and carrying on with something very similar we've got in the pipeline, that if someone at a very early age is identified to be on a harmful trajectory, then we can hopefully intervene at an earlier stage and try...to put the odds in their favor."

Sir Harpal Kumar, MBA, chief executive of Cancer Research UK, described the study as a "really interesting" approach to the study of the lifetime risk for obesity-related cancers, and he highlighted the importance of getting this message out to the general public.

"While there are no guarantees against the disease, keeping a healthy weight can help you stack the odds in your favor and has lots of other benefits too," he said in a statement. "Making small changes in eating, drinking, and taking exercise that you can stick with in the long term is a good way to get to a healthy weight and stay there."

This work was funded by Cancer Research UK as part of the National Awareness and Early Diagnosis Initiative and was supported by the Farr Institute. The authors have disclosed no relevant financial relationships.

NCRI Cancer Conference 2016. Poster session. Presented November 9, 2016. Abstract

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