Fat healthy, slim sick?!

As early as the 80s, patients were identified who showed no symptoms of an increased risk profile due to weight, despite being obese. Against a Body Mass Index beyond 30 kg/m², they exhibited neither high blood pressure nor insulin resistance, type 2 diabetes or a disruption to fat metabolism. For this reason, they gained the epithet of the metabolically healthy obese (MHO).

On the other hand, there are also people who are considered as being of normal weight by definition, with a BMI of below 25 kg/m², yet still exhibit the metabolism changes that would be expected in overweight people. For this reason, they are frequently also referred to as being of metabolically unhealthy normal weight (MUNW).

Why some overweight people are considered metabolically healthy, while a proportion of people of normal weight exhibit metabolic abnormalities, remains a subject of research. However, the basis is suspected to primarily be due to lifestyle factors along with genetic factors. In particular, a healthy diet, restricted nicotine and an active lifestyle appear to be decisive factors and can counter the negative consequences of excess weight. By contrast, an unhealthy lifestyle can have negative effects on health, even for people of normal weight. 

Due to the lack of standardised criteria, the figures for the incidence of MHO and MUNW vary. For example, for the metabolically healthy overweight, they range from just a few to over 50% of all overweight adults. Uncertainty also reigns for the proportion of metabolically unhealthy people of normal weight. A systematic overview published in 2008 by Wildman et al reached the conclusion that corresponding changes to the metabolism could be demonstrated in 23.5% of the people of normal weight who were subjects of the study. By contrast, other studies showed the proportion of MUNW in people of normal weight to only be a single-figure percentage range.

There is also uncertainty about the risk of heart and circulatory diseases, as current data is still incomplete and contradictory. It can be assumed that people with demonstrable metabolic irregularities, such as an insulin resistance, have a higher cardio-vascular risk than people of the same weight with health metabolisms. The relationship between MHO and MUNW remains unclear. Whilst some studies have reached the conclusion that MUNW have a higher risk than MHO, others state a conflicting conclusion. The development of consistent criteria and further research in the future may contribute to answering these questions.

Even if overweight people without metabolic anomalies have a lower risk of consequential diseases of obesity, research indicates that the metabolic situation can change for 30-50% of these people. These once metabolically healthy obese people can, over the years, become metabolically unhealthy and suffer from the corresponding consequences. This appears to be the case if there is a further increase in weight. 

Fundamentally, the recommended treatment for all overweight people is the same. Along with a reduction in weight, they will benefit from regular exercise and a balanced diet. The same measures are recommended in relation to metabolically unhealthy normal weight people. Identification of potentially endangered people with normal weight can, however, be difficult as they are often not aware of any risk.

The body composition should primarily be used as a guide for metabolic health, as the BMI is calculated by only using the body mass and body size, and thus can be easily falsified.

An athletic person with high muscle mass but a low proportion of fat can be classified as overweight by using the BMI, whilst an inactive person with a reduced muscle and increased fat quota will be considered as having normal weight.

Furthermore, the distribution of the fat tissue is crucial for metabolic health. In comparison with the somewhat passive subcutaneous fat tissue, the visceral fat in the body’s interior is very metabolically active. It distributes a large number of messenger substances, affects inflammatory processes and is a special risk factor for the occurrence of diseases of the metabolism, heart and circulatory system. Located in the core of the body, its dimensions can usually only be measured by very laborious methods, and its quantity can be increased even in the case of people with normal weight and a slim appearance.

The seca mBCA offers a fast and non-invasive alternative. Using bio-electrical impedance analysis, it can determine precisely the proportion of visceral fat in the body’s composition and is thus ideally suited to screening examinations of overweight people, but also those of normal weight. Increased visceral fat is thus identified early and can be treated before it leads to long-term damage to health.

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