Skip to main content

How to Improve Metabolic Health – The Facts

| By: Joseph Hearnshaw

Too often we may see the term ‘metabolism’ thrown about on the internet. Perhaps lines like; “they just have a very fast metabolism” is mentioned, which may well be true. Or the infamous “one trick Doctors don’t want you to know about!”, and adverts on “how to supercharge your metabolism” that still occasionally reappear on my Facebook feed (Yes Facebook, I know I need to shift my excess weight and lose some pounds, thank you!).

The word is used a lot, but do you really know what “metabolism” refers to? Or what your metabolic health actually is and why it matters? Or how to alter it in a beneficial way that meets your goals and needs? Most people don’t, or have a very limited knowledge of the topic.

What is Metabolism?

Put simply, Metabolism is just the process by which our bodies convert food and drink, typically mixed with oxygen, into usable energy [1] . Said usable energy is for processes that keep us alive. That includes breathing, pumping blood, keeping your hormone levels at a stable level, moving, thinking, and growing and repairing cells, among everything else that enables you to be ‘alive’. Below is an oversimplified and limited explanation of your metabolism, but it fits the scope of this article.

The number of calories our body requires at rest to do all of these things is the basal metabolic rate (BMR). The main determinant of how high your BMR is relative to other people is typically your muscle mass, as this tends to vary the most between peoples body composition and typically consumes the largest part of energy [2]–[5]. BMR also depends upon:

  • Body composition and size – The larger you are and the more muscle mass you have, the more energy you require at rest.
  • Biological Sex – Typically, eugonadal biological males have less body fat and more muscle mass than biological females at the same age and weight due to the influence of testosterone, which is comparatively much higher in males than females [6].
  • Age – As we age, we tend to lose fat-free mass, like muscle mass. More of our weight is adipose tissue (fat), which has a lower energy requirement [7]. We also seem to just ‘burn’ less, but this is generally due to the decrease in muscle mass [8].

But BMR is just what we burn at rest. The other factors that influence what we ‘burn’ or how much energy we expend per day include:

  • How our body uses food – Digestion, absorption, moving, and storing food is a calorically expensive process. Around 10% of calories eaten are used to digest food and store or use nutrients. Not all macronutrients (protein, fats, and carbohydrates) are equal in how much energy we can extract either thanks to diet-induced thermogenesis (DIT) [9].
    • DIT is around ~15-30% for protein, ~5-10% for Carbohydrates, and ~0-3% for fat – meaning that fat is the most ‘energy-efficient’ food in terms of energy cost of digesting the food; you get more usable energy (i.e. not wasted as heat or energy in the nutrient processing phase) from fat than Protein [9].
      • A high protein diet with lower carbohydrates will actually provide less ‘useful’ (i.e. not invested in processing said nutrient) energy than a higher carbohydrate or fat diet.
  • How much we move – Any movement, even the bouncing of my leg as I write this article, will use energy. Such is the nature of thermodynamics.
    • Obviously running versus me bouncing my leg a little is going to probably expend more energy due to increased power required (the measure of the amount of work that can be done in a given amount of time; more work done over time will require more force, ergo more energy required).

Any daily activity that isn’t exercise is called non-exercise activity thermogenesis (NEAT), like the bouncing of my foot or walking about the house. That includes gardening, fidgeting, cleaning and so on. It typically accounts for 100-800 kcals a day.

So we can expend more energy by moving more during the day, doing more exercise, and eating more protein and reducing other macronutrients. That’s if we want to expend more energy. We might not. Why might we not? Because our goals may differ. We can’t easily control the ‘speed’ of our metabolism, or our metabolic rate. But we can control how much energy we expend via physical activity and dietary changes, which in turn can alter our metabolic rate over time.

Something worth understanding is that the body tries to trend towards a net zero energy balance; a non-zero energy balance will mean an equal change in the energy content of the body in the form of changes in body weight and composition, which then subsequently alters energy expenditure. Positive energy balance will increase weight gain, but equally BMR due to increased lean and fat mass, and a decreased BMR will occur with negative energy balances triggering a reduction in body mass. It gets a lot more complex than this, but you’ll have probably heard of the saying ‘calories in versus calories out’ [10]. It’s a balancing act.

Why Does Metabolic Health Matter?

Eat more and you’ll likely gain weight, eat less or expend more energy than your ‘maintenance’ caloric requirement and you’ll lose weight. Where that’s sourced from depends on a number of factors, like your macronutrient composition, hormonal status, style of training, and genetics.

Western society tends to have high food availability with low physical activity due to office based work and minimal travel due to the use of transportation methods like cars, which require minimal input from us. That tends to promote a positive energy balance, where excess nutrients are stored in fat tissue (typically from fat/carbohydrates, rarely protein). This is bad for our metabolic health, which can give rise to an array of non-communicable diseases like obesity, type-2 diabetes, cardiovascular diseases, and more [11].

There is evidence that reduced body temperature favours longevity; negative energy balance tends to reduce body temperature. Furthermore, negative energy balance tends to improve longevity and health in general [12]. In short; reduce metabolic rate, slow the rate of aging. So, eat less and move more and you should get the fountain of youth. But this is only true to a point, where malnutrition and prolonged negative energy balance causes other diseases. It’s also extremely simplified again. We need to ensure we get adequate micronutrients and macronutrients for essential processes in our body, but not so much that we are storing excess weight as fat.

The topic of metabolic health is again, vastly more complex than this. We have the fact that being in an obese state causes a complex change in our metabolism such that we trend towards further worsening body composition is testament to that fact. Genetics play a fairly significant role, even the method by which you were born may play a role [13], [14]. Additionally, stress and mental state impact our behaviour and certain metabolic processes (and vice-versa), highlighting the interconnectedness of metabolic and mental health [15].

The point is that metabolic health is important to your overall health and longevity. There are also a large number of factors out of our control when it comes to metabolic health. But, most people can alter our diet and our physical activity. By doing so, we can improve our metabolic health, be it if you were previously anorexic and need to gain weight, or obese and need to lose it to return to a physiologically healthier state. Neither state is beneficial to your long term health.

Improving the Overweight to Obese State

Transitioning from an overweight or obese state can be extremely challenging, as it involves more than just the simplistic notion of “calories in vs. calories out”. Various factors come into play, such as dysregulated appetite control, altered gut hormones, impaired metabolism, and disrupted gut microbiota [16]. I understand first hand the intense hunger and constant fatigue that accompany this condition, creating a never-ending cycle. The desire to move less is driven by stress and appetite dysregulation, while increased blood glucose levels contribute to fatigue, creating a vicious cycle.

To address this situation, we need to either reduce energy intake below maintenance levels, or increase physical activity to enhance energy expenditure. It’s also crucial to address any hormone dysregulation that exacerbates the issue, such as hypothyroidism, which requires treatment. In an obesogenic state, we often observe an unfavourable hormonal profile that promotes fat accumulation, with lower testosterone levels in males and higher oestradiol levels in females.

Given the difficulties associated with eating less and the discomfort of increasing physical activity, we can explore alternative approaches to dieting. One such approach is intermittent fasting.

Intermittent fasting encompasses various methods, with the most common being a time-restricted feeding period. For example, the 16:8 method involves skipping breakfast and refraining from eating for a total of 16 hours from the last meal, leaving an 8-hour window for eating. Intermittent fasting works by naturally reducing calorie intake and creating a negative energy balance. To help manage energy and suppress appetite during the fasting period, you can have a black coffee, which provides a slight boost in energy and helps curb hunger.

In addition to its potential benefits on appetite hormone regulation [17], intermittent fasting can also contribute to improved adherence to a reduced calorie intake. Initially, there may be feelings of hunger, but over time, appetite regulation tends to improve (it’s important to stay consistent with the fasting routine). This can further support a decrease in overall caloric intake. For individuals with low sex hormone-binding globulin (SHBG) levels, intermittent fasting may be beneficial, as it has been shown to increase SHBG in non-lean individuals [18]. To enhance adherence during the fasting period, keeping oneself preoccupied with other tasks can be helpful.

However, it’s important to note that intermittent fasting should not be used as an excuse to consume more calorically dense foods, especially those high in fat content, and end up in a positive energy balance. The overall goal should still be to maintain a negative energy balance for weight management and improved metabolic health. So, we have to go further and we can do the following:

  • Increase protein intake by up to 30% of your macronutrient requirements.
  • Decrease fat intake, but ensure you consume a minimum of 30g per day, including omega-3, omega-6, and some saturated fats. Good sources include flaxseed oil, fatty fish, nuts, and fish oil.
  • Reduce carbohydrate intake to improve the T:E2 ratio, enhance overall health, and improve body composition. This also reduces the risk of certain non-communicable diseases.
  • Experiment with your carbohydrate intake to find what works best for you based on genetics and health conditions. Individuals with type-2 diabetic family members may benefit from a low carbohydrate diet.
  • Use a food scale and tracking app to accurately estimate calorie content. Weigh dry foods like rice and pasta, as nutritional information is often provided for cooked portions.
  • Eliminate junk food, which is high in sugar and fat and worsens appetite. Opt for healthier options to prevent weight gain.
  • Reduce calorie intake by approximately 5% to support weight maintenance.
  • Increase energy expenditure through exercise or increasing non-exercise activity like household chores.
  • Consume a minimum of 30g of fibre per day through foods like green vegetables, beans, legumes, cereals, nuts, carrots, oats, avocados, fruits, and consider supplements like psyllium husk.
  • Slow down your eating pace to feel fuller and consume fewer calories.
  • Avoid distractions while eating, such as watching TV or multitasking, to improve satiety.
  • Consider reducing the frequency of meals and establish regular eating times to reduce appetite and weight gain risk.
  • Track your calorie intake using an app for better dietary adherence.
  • Incorporate resistance training into your routine to build muscle mass, increase energy expenditure, and regulate appetite.
  • Opt for well-balanced meals with a combination of carbohydrates, protein, and fats to feel satiated and obtain essential micronutrients. A higher protein diet can aid in appetite regulation and increase the thermic effect of food (DIT).
  • For complex situations like diabetes or gluten intolerance, consult a medical professional to customise a diet and exercise plan.
  • Increase non-exercise activity, like walking to nearby locations instead of driving or taking short breaks for walks during desk jobs.

These tools can help improve metabolic health for overweight or obese individuals by reducing energy balance. Although it may be challenging initially, it becomes easier over time. It’s important to note that as your body adapts to a net zero energy balance, you will need to gradually decrease energy intake or increase energy expenditure. When you reach a plateau in weight loss, eat at maintenance for two weeks to restore homeostasis and then resume the caloric deficit. This “reset” helps regulate major metabolic hormones that could otherwise impede further fat loss.

Improving the Underweight State

Going from an underweight state often requires medical assistance. If you are anorexic, you must seek professional medical help. If otherwise generally underweight from chronically being a negative energy balance, you probably have high SHBG, low sex-steroid hormones, low thyroid hormone, the list goes on. You’d benefit from increasing your energy intake and could do the following:

  • Track your calorie intake using an app, aiming for a slightly higher intake than your current maintenance requirements until you reach a specific weight goal.
  • Increase the consumption of calorically dense foods while ensuring they meet your macro and micronutrient needs. For example, include fattier meat or fish cuts, more nuts, and additional fruits in your diet.
  • Consume meals at a faster pace to increase calorie intake per sitting.
  • Eat more frequently throughout the day.
  • Ensure that your meals still include adequate fibre and a variety of vegetables and fruits.
  • Incorporate weightlifting into your routine, similar to what you would do in an obesogenic state. Additionally, engage in cardiovascular exercises, making sure to compensate for the energy expended through food consumption.
  • Monitor your daily activity using smartwatches or phones, as your non-exercise activity thermogenesis (NEAT) may be higher due to your job. If you burn more than you consume, eat more!
  • Consider consulting a nutritionist for personalised guidance and support.

Tools to Help You

You can calculate your approximate BMR here. You should also calculate your  total daily energy expenditure (how much energy you burn a day when accounting for exercise). If you don’t know your bodyfat percentage, you can estimate it via the Navy method, albeit this isn’t an accurate method. But if you are getting inBody scans at the clinic, you will have a significantly more accurate value.

Several apps (MyfitnessPal, Lifesum) exist online to help track calorie intake, with some focusing on behavioural alterations and providing meal recommendations like Noom.

Here you can find a list of foods high in omega-3 & 6. Here is a list of foods high in fibre. Here is a list of foods which are high in nutrient density. Before you buy a food, look at its nutritional information.

Ensure your diet meets your daily nutritional requirements, be it vegetarianism, veganism, pescetarianism – you can get adequate macro and micronutrients with each dietary type but you must record it and ensure you get the right kinds of foods. For example, Vegans notoriously lack iron in their diet, which is easily remedied with tofu, lentils, chickpeas, and much more. You can search for the nutritional value of foods using standard calorie tracking apps, and many apps even offer barcode scanning for convenience.

The Søberg Principle

Something else that is still debated in the scientific community is heat and cold exposure and its effects on metabolic health. The Søberg principle, created by Dr. Susanna Søberg with her research [15],  is simply the following:

When using deliberate cold exposure to increase your metabolism, minimize hot showers & sauna after the last cold exposure. Forcing your body to re-warm on its own is a major component of the metabolism & brown-fat (healthy, thermogenic fat) stimulation.

What’s the verdict on cold therapy? Well, the activation of brown adipose tissue (BAT) in cold water immersion (CWI) and cold exposure helps regulate body temperature. It also improves blood pressure, vascular health, and immune response. BAT is something that adults are generally lacking in (babies have a lot of it), but it plays a role not only in thermogenesis, but also metabolic health; it improves insulin sensitivity, increases glucose-uptake, and free-fatty acid uptake too [16]. Additionally, by means of raising a hormone produced by fat called Adiponectin, cold exposure (via the process of shivering and nonshivering thermogenesis) may promote increased longevity [17].  With that said, more research is still needed. One thing is for sure – cold exposure tends to increase energy intake (ever wonder why you’re hungrier when it’s colder?), at least in an acute setting (so keep that in mind) [18].

As for heat exposure, it also may promote increased longevity due to an increase in heat shock proteins being produced [19]. Brief exposure to sauna bathing (<1h) tends to reduce blood pressure, improve arterial stiffness, and when done repeatedly, it can upregulate several beneficial enzymes and pathways, resulting in greater stress tolerance, and improved health [20]. It also reduces energy intake and helps suppress hunger. Why does it appear to improve metabolic health? Most likely due to increasing the expression of something called AMPK; as AMPK activity increases, we upregulate metabolic pathways such as glycogenolysis and lipolysis, in addition to having other functions. Metformin, used to control Type 2 Diabetes Mellitus, activates AMPK – so does aerobic exercise. But, more research is necessitated.

Dr. Søberg recommends the following protocol [21]:

  1. Winter swimming 2-3 x per week for 3-6 minutes, or ~11 minutes a week
  2. Sauna 2-3 x per week totaling 19-28 minutes, or ~ 57 minutes per week

But this is not for the faint hearted! Not everyone can swim (or they have a fear of deep water, like I do), nor can everyone tolerate cold or heat exposure, particularly if you have health conditions that could pose an issue. As always, discuss with your GP. If you aren’t a swimmer, look towards ice baths or cold showers instead. Emulating the Nordic tradition of embracing such practices may lead to numerous benefits, but it is essential to recognise (again!) that more research is needed to establish the full extent of these advantages [21].


I think that finding the dietary style that works best for an individual is important, as different approaches suit different people. However, regardless of the chosen dietary style, the principles of energy balance will always apply. Factors such as genetics, stress, active energy expenditure, NEAT, drugs, and overall health can and will influence energy balance, but we still have some level of control over it. Some more than others, but nonetheless we have some control.

Maintaining a healthy body composition (note – healthy, not becoming an IFBB pro) is indeed crucial for good metabolic health, which in turn can contribute to longevity and overall well-being. The list of strategies provided is not exhaustive, but it serves as a starting point to help individuals understand how they can make positive changes for their health.

Acquiring knowledge in the field of nutrition is a valuable first step towards improving body composition and ultimately metabolic health. Consulting a nutritionist can provide further guidance and personalised support if needed. It’s important to remember that everyone’s journey is unique, and seeking professional help can be beneficial in navigating individual circumstances and achieving specific health goals.


[1]  ‘Can you boost your metabolism?’, Mayo Clinic. (accessed Jul. 15, 2023).

[2]  E. G. A. H. van Mil, K. R. Westerterp, A. D. M. Kester, and W. H. M. Saris, ‘Energy metabolism in relation to body composition and gender in adolescents’, Arch. Dis. Child., vol. 85, no. 1, pp. 73–78, Jul. 2001, doi: 10.1136/adc.85.1.73.

[3]  J. C. Aristizabal et al., ‘Effect of resistance training on resting metabolic rate and its estimation by a dual-energy X-ray absorptiometry metabolic map’, Eur. J. Clin. Nutr., vol. 69, no. 7, Art. no. 7, Jul. 2015, doi: 10.1038/ejcn.2014.216.

[4]  ‘Skeletal muscle metabolism is a major determinant of resting energy expenditure. – PMC’. (accessed Jul. 15, 2023).

[5]  B. K. McNab, ‘What determines the basal rate of metabolism?’, J. Exp. Biol., vol. 222, no. Pt 15, p. jeb205591, Aug. 2019, doi: 10.1242/jeb.205591.

[6]  D. J. Handelsman, A. L. Hirschberg, and S. Bermon, ‘Circulating Testosterone as the Hormonal Basis of Sex Differences in Athletic Performance’, Endocr. Rev., vol. 39, no. 5, pp. 803–829, Jul. 2018, doi: 10.1210/er.2018-00020.

[7]  Z. Wang et al., ‘Specific metabolic rates of major organs and tissues across adulthood: evaluation by mechanistic model of resting energy expenditure1234’, Am. J. Clin. Nutr., vol. 92, no. 6, pp. 1369–1377, Dec. 2010, doi: 10.3945/ajcn.2010.29885.

[8]  H. Shimokata and F. Kuzuya, ‘[Aging, basal metabolic rate, and nutrition]’, Nihon Ronen Igakkai Zasshi Jpn. J. Geriatr., vol. 30, no. 7, pp. 572–576, Jul. 1993, doi: 10.3143/geriatrics.30.572.

[9]  D. H. Pesta and V. T. Samuel, ‘A high-protein diet for reducing body fat: mechanisms and possible caveats’, Nutr. Metab., vol. 11, p. 53, Nov. 2014, doi: 10.1186/1743-7075-11-53.

[10] Y. Y. Lam and E. Ravussin, ‘Analysis of energy metabolism in humans: A review of methodologies’, Mol. Metab., vol. 5, no. 11, pp. 1057–1071, Sep. 2016, doi: 10.1016/j.molmet.2016.09.005.

[11] Z. Song, A. M. Xiaoli, and F. Yang, ‘Regulation and Metabolic Significance of De Novo Lipogenesis in Adipose Tissues’, Nutrients, vol. 10, no. 10, p. 1383, Sep. 2018, doi: 10.3390/nu10101383.

[12] A. Bartke, S. Brannan, E. Hascup, K. Hascup, and J. Darcy, ‘Energy Metabolism and Aging’, World J. Mens Health, vol. 39, no. 2, pp. 222–232, Apr. 2021, doi: 10.5534/wjmh.200112.

[13] G. D. P. Coelho, L. F. A. Ayres, D. S. Barreto, B. D. Henriques, M. R. M. C. Prado, and C. M. D. Passos, ‘Acquisition of microbiota according to the type of birth: an integrative review’, Rev. Lat. Am. Enfermagem, vol. 29, p. e3446, doi: 10.1590/1518.8345.4466.3446.

[14] J. MINAMI et al., ‘Effects of Bifidobacterium breve B-3 on body fat reductions in pre-obese adults: a randomized, double-blind, placebo-controlled trial’, Biosci. Microbiota Food Health, vol. 37, no. 3, pp. 67–75, 2018, doi: 10.12938/bmfh.18-001.

[15] C. Deng and J. K. Yao, ‘Editorial: Metabolic Disturbances in Mental Illness: Neuropathogenetic Mechanisms and Therapeutic Implications’, Front. Neurosci., vol. 14, p. 21, Jan. 2020, doi: 10.3389/fnins.2020.00021.

[16] A. Pucci and R. L. Batterham, ‘Endocrinology of the Gut and the Regulation of Body Weight and Metabolism’, in Endotext [Internet],, Inc., 2020. Accessed: Jul. 15, 2023. [Online]. Available:

[17] E. Ravussin, R. A. Beyl, E. Poggiogalle, D. S. Hsia, and C. M. Peterson, ‘Early Time-Restricted Feeding Reduces Appetite and Increases Fat Oxidation But Does Not Affect Energy Expenditure in Humans’, Obes. Silver Spring Md, vol. 27, no. 8, pp. 1244–1254, Aug. 2019, doi: 10.1002/oby.22518.

[18] S. Cienfuegos et al., ‘Effect of Intermittent Fasting on Reproductive Hormone Levels in Females and Males: A Review of Human Trials’, Nutrients, vol. 14, no. 11, p. 2343, Jun. 2022, doi: 10.3390/nu14112343.

[19] G. Argyrakopoulou, S. Simati, G. Dimitriadis, and A. Kokkinos, ‘How Important Is Eating Rate in the Physiological Response to Food Intake, Control of Body Weight, and Glycemia?’, Nutrients, vol. 12, no. 6, p. 1734, Jun. 2020, doi: 10.3390/nu12061734.

[20] L. Braude and R. Stevenson, ‘Watching television while eating increases energy intake. Examining the mechanisms in female participants’, Appetite, vol. 76, Jan. 2014, doi: 10.1016/j.appet.2014.01.005.

[21] A. Paoli, G. Tinsley, A. Bianco, and T. Moro, ‘The Influence of Meal Frequency and Timing on Health in Humans: The Role of Fasting’, Nutrients, vol. 11, no. 4, p. 719, Mar. 2019, doi: 10.3390/nu11040719.

[22] J. S. Ingels, R. Misra, J. Stewart, B. Lucke-Wold, and S. Shawley-Brzoska, ‘The Effect of Adherence to Dietary Tracking on Weight Loss: Using HLM to Model Weight Loss over Time’, J. Diabetes Res., vol. 2017, p. 6951495, 2017, doi: 10.1155/2017/6951495.

[23] ‘ResearchHub | Open Science Community’, ResearchHub. https:// (accessed Jul. 20, 2023).

[24] C. Huo et al., ‘Effect of Acute Cold Exposure on Energy Metabolism and Activity of Brown Adipose Tissue in Humans: A Systematic Review and Meta-Analysis’, Front. Physiol., vol. 13, p. 917084, Jun. 2022, doi: 10.3389/fphys.2022.917084.

[25] D. Espeland, L. de Weerd, and J. B. Mercer, ‘Health effects of voluntary exposure to cold water – a continuing subject of debate’, Int. J. Circumpolar Health, vol. 81, no. 1, p. 2111789, doi: 10.1080/22423982.2022.2111789.

[26] J. Millet et al., ‘Effects of Acute Heat and Cold Exposures at Rest or during Exercise on Subsequent Energy Intake: A Systematic Review and Meta-Analysis’, Nutrients, vol. 13, no. 10, p. 3424, Sep. 2021, doi: 10.3390/nu13103424.

[27] M. Lagisz, K. L. Hector, and S. Nakagawa, ‘Life extension after heat shock exposure: assessing meta-analytic evidence for hormesis’, Ageing Res. Rev., vol. 12, no. 2, pp. 653–660, Mar. 2013, doi: 10.1016/j.arr.2013.03.005.

[28] K. N. Henderson, L. G. Killen, E. K. O’Neal, and H. S. Waldman, ‘The Cardiometabolic Health Benefits of Sauna Exposure in Individuals with High-Stress Occupations. A Mechanistic Review’, Int. J. Environ. Res. Public. Health, vol. 18, no. 3, p. 1105, Feb. 2021, doi: 10.3390/ijerph18031105.

[29] S. Søberg et al., ‘Altered brown fat thermoregulation and enhanced cold-induced thermogenesis in young, healthy, winter-swimming men’, Cell Rep. Med., vol. 2, no. 10, p. 100408, Oct. 2021, doi: 10.1016/j.xcrm.2021.100408.