Entry standards for both the armed forces and the police have included measures of height and weight as surrogates for operational fitness. Body Mass Index (BMI) is a practical measurement that has been shown to correlate well with outcomes of obesity, such as high blood pressure and insulin-mediated glucose uptake. However, the military have found that use of BMI to assess obesity may be problematic because an increase in BMI might relate to an increase in the fat-free mass (largely muscle) but not fat mass. A specificity of about 0.96 means that some people with a high BMI are misclassified as obese, although the number of false positives will be small. In addition, BMI has a sensitivity of approximately 0.5 meaning that it does not detect almost half of people with high body fat levels.

Several high-profile drone incursions above military facilities or sensitive facilities like nuclear power plants have shown that UAVs are already skirting air defense systems and pose a new threat for which there is no easy solution.

"A quarter of Britain’s soldiers are classed as 'dangerously' overweight in the past five years, with more than 5000 discharged for being overweight or obese, since 2010” screams the  Mail on Sunday.

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"For instance, in environmental monitoring over remote locations or long-endurance surveillance missions where GPS might be unavailable or compromised, this technology offers a valuable new capability," Chahl said.

Such a capability could be used to operate drones in areas where GPS signals are jammed or degraded due to electronic warfare. This type of warfare targets the electromagnetic spectrum, through which radio signals and other emissions pass.

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The new system combines visual observations of the stars with standard autopilot technologies. In tests of the system using a fixed-wing UAV, researchers were able to pinpoint the drone's position within 2.5 miles (4 kilometers).

With that being the case, creating small, inexpensive celestial navigation systems will likely only accelerate the already-burgeoning future of drone warfare.

It is also important not to discriminate unfairly against applicants. Whilst under current legislation employees are not protected from discrimination on the grounds of obesity alone, there is now case law that has determined that being severely overweight, that is with a BMI more than 30 kgm2, can be a disability, if it affects ability to work. Long-term disability caused by obesity, such as impaired mobility, should be protected by disability laws.

A new celestial navigation system designed for drones could make them harder to detect by eliminating the need for GPS signal emissions.

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Despite entry thresholds for height and weight, a recent FOI request revealed that, between January 1 2019 and March 31 2022, 59,219 UK armed forces personnel had a recorded body composition measurement of increased risk of ill health (overweight). Medical discharges for the year 2022/23 reveal that the principal causes were musculoskeletal and mental health, which was in line with previous years.

Brett is curious about emerging aerospace technologies, alternative launch concepts, military space developments and uncrewed aircraft systems. Brett's work has appeared on Scientific American, The War Zone, Popular Science, the History Channel, Science Discovery and more. Brett has English degrees from Clemson University and the University of North Carolina at Charlotte. In his free time, Brett enjoys skywatching throughout the dark skies of the Appalachian mountains.

Similarly, using QRisk an otherwise healthy 25-year old male with a BMI of 35 – 40 kgm2 has a risk of having a heart attack or stroke over the next 10 years of 0.2%. Is that sufficient to reject an applicant? Does having a high BMI affect aerobic capacity? A study in the US, where Cooper tests (push ups, sit ups, sit and reach test and a 2.4 Km run) were introduced to assess physical fitness, found that, whilst a 1% incremental increase in body fat was associated with a decrease in performance, it did not impair candidates from meeting the threshold for fitness. The current UK police job-related fitness test (bleep test) is less demanding than the Cooper tests.

In the absence of other information, obesity does not appear to be a direct cause of medical discharges. Secondary disability due to obesity is a possible reason for a musculoskeletal medical discharge. It might be the case that the other health conditions have contributed to the prevalence of overweight personnel? It is unclear as to the data source for the 5000 discharges due to being overweight or obese.

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A study in the Lancet found that, compared to a healthy baseline population, increased risks of all-cause mortality increased with BMI such that a BMI of 30 – 34.9 kgm2 increased the risk by 45% and a BMI of 35 – 39.9 kgm2 increased the risk by 94%. These are hazard ratios meaning that an increase of 94% is an almost doubling of risk. Is that sufficient to reject an applicant?

"Unlike traditional star-based navigation systems, which are often complex, heavy and costly, our system is simpler, lighter and does not need stabilization hardware, making it suitable for smaller drones," said Samuel Teague of the University of South Australia (UniSA), in a statement.

There is evidence that metabolic syndrome is prevalent in law enforcement and appears to be increasing. A study in the US following the 2001 World Trade Centre (WTC) attacks found that approximately 25% law enforcement officers who worked at the WTC site met the criteria for metabolic syndrome.

But on the other hand, the capability to operate drones without the need to transmit and receive GPS signals could make it harder for militaries and other security forces to detect and defend against UAVs.

The researchers behind this new celestial navigation system say it could help not only with military missions, but also in peacetime operations like Earth observation.

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And as the ongoing war in Ukraine shows, the future of air warfare will likely move away from large, expensive fighter jets crewed by human pilots and toward smaller, less expensive drones that are easy to replace.

Measurement of waist circumference is another option and the military have moved to a new approach to assessing obesity – body composition measurement, which combines BMI and waist circumference measurements. The risk of obesity in the UK armed forces has been shown to rise with age and in the lower ranks, for both men and women. The risk of obesity in officers an d the Royal Marines was less than for other study participants when a threshold of 27.5 Kg/m2 for BMI and waist circumference of 94 cm. (men) and 84 cm. (women) was used. The explanation was that the muscle mass was greater in these groups.

A former 'army chief' is quoted as saying “I believe that young overweight soldiers should be monitored very closely and if their weight cannot be controlled, they should be discharged.” There is a concern that dietary behaviour does not change in line with changes in duties and lifestyle. The current situation has been described as a failure of leadership by 'top brass'.

If an applicant has no other health problems and is capable of passing the physical fitness and ability tests, why should s/he be denied entrance? Any health issues related to an elevated BMI, excessive waist measurement or other anthropomorphic test, is likely to develop later in life, after most military or police personnel have left the service.

"We have developed a navigation method that’s resilient, independent of external signals, and achievable with low-cost, easily accessible components. This makes it applicable to a variety of UAVs, from commercial drones to more advanced defense applications," UniSA scientist Javaan Chahl said in the statement.

Such a system could make drones harder to detect and more resistant to jamming attacks that deny or disrupt GPS signals, one of the most common forms of long-distance navigation and positioning.

As an emergency service, there are standards of fitness to ensure that officers are deployable to the front line. The job-related fitness test, a core component of assessing fitness of recruits, as well as monitoring on-going fitness for personal safety training, is used to measure cardio-respiratory fitness. However, following recruitment, obesity measurement data is not routinely collected for police officer populations. Whereas MOD statistics can be interrogated to provide intelligence on the prevalence of obesity, type 2 diabetes and high blood pressure, we are largely ignorant about these important measure in UK policing at a national level.

Another prospective study of Chinese police officers concluded that work stresses are a risk factor for the development of metabolic syndrome. The National Police Wellbeing Service will be exploring how to address this issue through developing health assessments utilising the OK vans and the establishment of a police health observatory.

In conclusion, there is clear evidence that obesity in the armed forces is increasing, and it now affects about 13% population. Questions have been posed about effective leadership and a commitment to the health and wellbeing strategy for the UK armed forces. Similar workforce data for UK policing is lacking. However, it seems likely that obesity may also be a problem that should be addressed. This should not be conflated with the performance of entrance measurements of obesity, which should only relate to the ability to perform the role of a police constable.

Scientists from the University of South Australia have developed a new navigation system that allows uncrewed aerial vehicles (UAVs) — or drones, as they're more commonly known — to sense their location based on the stars in the night sky.

Celestial navigation, as this technique is known, has been used by humanity for thousands of years. Aircraft and spacecraft have used similar systems for decades, but this new system is designed to be low-cost and lightweight enough to be used on smaller drones, according to the researchers developing it.

This blog has been written by Prof John Harrison the National Police Chief Medical Officer following the recent update sent to forces from the College of Policing on how to use BMI assessments during police officer recruitment.

New guidance on medical standards for UK policing will be published in 2024. They will update existing Home Office standards from 2004. In advance of this, guidance has been shared with practitioners working in policing on the use of BMI in recruitment.

Russia has repeatedly jammed GPS signals in Ukraine throughout its nearly three-year invasion of the nation, using mobile jammers mounted on trucks. The U.S. Space Force has been developing and testing similar systems of its own.

Evidence suggests, therefore, that the use of the BMI as a criterion of fitness for police officer applicants, on its own, is inappropriate. A pre-placement health assessment should address the relevance of current or previous health conditions and their relevance to the ability to perform the functional requirements of the job.