I asked chat gpt about this since my own experience is definently that immigrants (from middle east) are usually not slim.

Here is a what it said:

Yes — there is credible evidence that immigration has been associated with changes in obesity levels in Europe (and other high-income regions) over the past ~20 years, though causality is complex and effects vary by group. Here is a breakdown of what the research shows, the mechanisms, and important caveats.

✅ What the evidence shows

A systematic review on migrants found: “migrants may arrive in new countries with a health advantage … but unhealthy weight gain in migrant populations may lead to similar or greater obesity risk compared with native populations 10-15 years after migration.”

In Norwegian Institute of Public Health data: children (~8 years) with an immigrant background in Norway had higher prevalence of overweight/obesity than children with no immigrant background.

A meta-analysis found among immigrants/refugees: overweight prevalence ~37%, obesity ~23% across studies.

A study of pre-pregnancy obesity in immigrant vs non-immigrant women in Norway found that obesity increased in both groups over time; immigrant status did not protect against the upward trend.

A study of immigrant adolescents in Spain found that prevalence of overweight + obesity among Latin-American immigrants was higher than that of Eastern-European immigrant adolescents; and higher than the native Spanish adolescents in one sample.

🔍 Mechanisms and contributing factors

Several plausible mechanisms by which immigration could influence obesity trends:

Acculturation / lifestyle change: Migrants from countries with lower obesity prevalence may adopt host-country dietary patterns (often higher in processed food, sugar, fat) and sedentary behaviours over time.

Socio-economic position (SEP): Many immigrant populations face lower SEP, which correlates with higher obesity risk in many high-income countries. However, in the Norwegian children study parental education (a SEP proxy) did not fully explain the higher obesity prevalence among immigrant background children.

Pre-migration exposure + selection: Some migrants come from countries with rising obesity rates; previous exposures may carry risk. The migration “selection” effect (healthier people migrating) may diminish over time.

Time since migration: The evidence suggests obesity risk rises with length of residency in the host country.

Cultural, environmental, built-environment factors: Access to healthy food, physical activity environments, language/cultural barriers in health promotion can affect immigrant populations disproportionately.

⚠️ Important caveats & limitations

The research often focuses on immigrant groups specifically, not purely on the national obesity rate aggregated across all residents. So linking immigration → national obesity rate rise requires caution (there are many confounders).

Longitudinal, causally-attributed studies are fewer. Many are cross-sectional (immigrant vs non-immigrant at one time).

Variation across origin country, host country, generation (first vs second), gender, age-group is large. Immigrants from some regions show higher risk than others.

The effect size attributable to immigration, compared to other drivers (e.g., general diet change, sedentary lifestyle, macro socioeconomic trends) is unclear. For example, the study of France/Spain found that most of the difference in overweight between immigrants and natives was due to “coefficients” (i.e., unobserved factors) rather than observable characteristics.

Data for the 20-year span in some places is limited.

📋 Summary statement

Immigration into European/high-income countries is associated with higher obesity risk in immigrant sub-populations and may contribute to national obesity trends — especially via lifestyle change, socio-economic disadvantage, and acculturation effects. But immigration is one of many interacting factors; it is not the sole or dominant driver of the obesity rise in Europe.

If you like, I can check quantitatively how much of the obesity rise in specific European countries can be statistically attributed to immigration (versus other factors).

Alabama and Massachusetts are definitely a lot closer culturally than Sweden and Italy