The odds of having obesity in middle age are sixfold higher if both parents also had obesity in middle age, showed data that shed some light on the nature of intergenerational patterns of obesity in families.
Findings are drawn from an ongoing population-based health study by Mari Mikkelsen, MSc, lead researcher from the UiT Arctic University of Norway, Tromsø, Norway. Mikkelsen will present her work at the upcoming European Congress on Obesity to be held in Venice on May 12-15, 2024.
Evidence on the intergenerational transmission of obesity in adult age is scarce, said Mikkelsen, but she noted that other researchers had speculated that similar dietary and exercise habits run in families when parents and children live under one roof resulting in similar body mass index (BMI).
"We suspected obesity would also follow children into middle age," she said, highlighting that their study found this to be true. "Children whose parents lived with obesity are much more likely to be in living with obesity themselves when they are in their 40s and 50s, long after they have left home."
"Our findings show that the intergenerational transmission of obesity is also present in adulthood [middle-age] and underlines the importance of prevention and treatment of obesity because we know that obesity increases the risk of disease, ill health, and premature death, so it is highly relevant to investigate whether the known association between parents' and their children's BMI is also present in adult age," Mikkelsen told Medscape Medical News.
Asked whether this indicated anything about the contribution of genetics and/or environmental factors in precipitating obesity, she pointed out that the study doesn't address the contribution made by genetics to this risk in the child, but Mikkelsen suggested, "we are most likely looking at a combination of the two with other research showing that genes affect our susceptibility to weight gain when encountering obesogenic environments."
Generational Population-Based Study
Data were drawn from the Tromsø Study, an ongoing population-based health study, initiated in 1974. It is composed of seven repeated surveys and more than 45,000 individuals. Here, in the study led by Mikkelsen, data from middle-aged adults who participated in Tromsø7 (2015-2016) were linked to their parents' data from the Tromsø4 (1994-1995) survey, resulting in a dataset with 2068 complete trios, all aged 40-59 years. Height and weight were measured for all participants, as well as other information including physical activity level, education, and diet.
The associations of parental BMI and obesity status were compared with those of their children, all in middle age. Regarding obesity, the model generated the association of the mother's and father's obesity status (BMI, > 30) with the odds of obesity in the offspring when one or both parents lived with obesity, compared with both having normal weight. Odds ratios (ORs) were adjusted for offspring's sex, parents' and offspring's age, education, and physical activity level.
Parents' Middle-Aged BMI and Obesity Status Reflected by Child at Middle Age
Evidence was found of a strong association between parents' BMIs in middle age and that of their offspring at the same age. One SD (four units of BMI) increase in maternal and paternal BMI was associated with 0.80 (95% CI, 0.60-1.00) and 0.74 (95% CI, 0.55-0.93) units increase in their adult child's BMI, respectively.
"These results tell us that adults [of middle-age] tend to have higher BMI if their parents have higher BMI during middle age," emphasized Mikkelsen.
When obesity (BMI, ≥ 30) was looked at specifically, the relationship between parents and children was also strong. If both parents had obesity in middle age, their children had six times higher odds of living with obesity in middle age (OR, 6.01; 95% CI, 2.85-12.66) than adults with both parents in the normal weight range (BMI, 18.5-24.9).
The odds were also raised when only one parent lived with obesity. When only the mother lived with obesity, the offspring had 3.44 times higher odds of living with obesity themselves. The corresponding number for fathers was 3.74.
"These findings also lay the foundation for research into factors that influence the intergenerational transmission of obesity and that can be targeted to prevent offspring from spending their whole life affected by obesity," remarked Mikkelsen.
Mikkelsen has not declared any relevant financial disclosures.
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