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Why You Shouldn’t Take Dietary Advice From Your PT

If you have been trying to lose weight recently, either for heart health, general health, a sports goal or just to look or feel better, you may be one of thousands of people that have either signed-up to a programme with a PT or enrolled on an online programme (for 8 or 12 weeks generally).

If you have you will no doubt hear the simple and often repeated exclamation relating to fat loss directed at you through a social media post, or video, or face-to-face……..”It’s all about calories in v calories out!” Or “You just need to be in a calorie deficit!” or words to that effect.

This is a sign that your PT probably don’t know much about metabolism or good health and they are likely to be hiding that behind a forcefully expressed mantra of simplicity.

In fact many PT’s (but not all) will have never needed to lose weight, and may have always been slim, active and metabolically flexible since childhood, and would have very little understanding of weight-loss strategies and their implementation for older, compromised metabolisms such as those of a heart-disease sufferor.

Despite being a qualified fitness trainer, and having a lot of experience and knowledge around exercise & nutrition, I joined an online PT programme after I had recovered from my hospital procedure following a heart attack in 2019.

I wanted to be part of an accountable group of like-minded people that were transforming their health and improving their body-mass, and I needed to drop a stone to get to my perfect weight. So I signed-up to an 8-week body transformation course.

The 8 week challenge was well run, and involved following a number of training regimes delivered through an app, as well as tracking macro-nutrients and calories used and consumed through My Fitness Pal.

In My Fitness Pal we were given targets for calorie consumption for each day, that follow the basic rules of thumb used by the industry. This means providing you with your daily calorie usage numbers and then asking you to track them on the app and ensure that at the end of each week (or day preferably) you are in a deficit. ie. You use more calories that you consume.

The Standard formula states that for every 3,500 calories in deficit you become, you will lose 1 lb of body-fat.

The premise for this massive over-simplification of the human metabolic system, is that if you are eating less calories than you consume then your body will not have enough free dietary glucose for energy and it will release energy from fat cells. Additionally, the estimate for the amount of calorific energy in each 1 lb of fat is 3,500 calories, therefore, if you have a 500 calorie deficit per day, over a week you will lose 1 lb of fat.

This sounds credible, and is somewhat scientific in nature, but it is a combination of estimates, applied to averages, and linked to assumptions that don’t really work in real life for most people. Some will find benefit initially, but for most they may do the maths and conclude that their final weight-loss number doesn’t quite equate to the sum of the effort they have made.

My experience on the programme fitted that description.

After the first 3 weeks of strict adherence to the training and eating pattern, I hadn’t lost any weight. I had actually gained 1 lb, but felt great.

After the first 6 weeks I had gained another lb, but was noticeable stronger and fitter.

At the end of the 8 weeks I was about 1 lb lighter than when I started.

Whilst this probably sounds like a terrible result to you, and compared to some of the larger participants that lost over 10lbs it might look poor, I was OK about it.

I was much fitter and stronger than when I had started, and I knew from personal experience (and some clever scales) that my muscle mass had increased and I had actually probably lost about 4 lbs of fat.

I did, however, have a major gripe…and it was this:

At the end of the programme, to give a little hope to those who like me…had worked hard but not seen a massive change in bodyweight, I messaged the group.

I said that despite creating a calorie deficit to provide a greater fat-loss, I had in fact only dropped 1 lb on the scales, but that these things are not generally linear and one should use the programme as the start of a lifestyle change rather than just 8 weeks of dieting.

The response I received, from both the PT running the programme and his army of avid followers was pretty shocking. Whilst the PT diplomatically hinted that I probably hadn’t been following the calorie deficit properly, his supporters were less kind…telling me I was lying to myself and others about being in a deficit, claiming that it was impossible not to have lost the weight had I been doing as instructed.

I explained to some of them, that over some periods of the programme I had been on a tennis holiday playing 5 hours a day, walking hills, swimming and following the weights regimes whilst eating in some cases 1,000 calories less per day than the allowance, but still the vitriol kept coming. “You don’t know how to count!” “You are a liar!”.

In case you are one of the people for whom calories in v calories out doesn’t seem to work, take heart. It’s not you! It’s them!

Every process in our bodies is directed by hormones...when we feel hungry and when we feel full (no that isn’t because your stomach is empty or is a hormone telling you to eat or stop eating!. Similarly when to release fat from cells and when to store it, whether to preserve fat and break-down muscle, whether to shut down your immune system or to increase its responsiveness.

All hormones. And there are hundreds and hundreds of hormonal processes, that when dysfunctional can do anything from cause heart-disease and cancer to arthritis and dementia....and yes can prevent you losing weight/bodyfat.

Your PT will probably advise that you eat between 200 to 300 calories a day less than you utilise.

Here are a few things that would potentially cause an issue with a PT’s over simplistic view of fat-loss.

  • Daily calorie expenditure estimates based on height, weight, sex, etc can be wildly inaccurate. They are based on generic formulas, simplified and not exact.

A 2005 meta-analysis study on BMR* showed that when controlling all factors of metabolic rate, there is still a 26% unknown variance between people. Essentially, an average person eating an average diet will likely have expected BMR values, but there are factors that are still not understood that determines BMR precisely.

  • Food calorie estimates can be inaccurate (by up to 20% in either direction) and still be allowable on food descriptions.

The FDA allows food companies wide latitude in the accuracy of the calories listed on package labels—20 percent in either direction. That means if a label says 200 calories per serving, it could be 240 calories or 160 calories or anything in between. What’s more, the FDA doesn’t do any systematic policing of labels to ensure that calorie counts meet even that lax degree of accuracy. The responsibility for label accuracy remains with the food companies, from national manufacturers to regional or local vendors. It basically works on the honor system.

  • Food weight measurements can be inaccurate on packaging.

  • Our base metabolic rate can fluctuate massively throughout days and weeks depending on a variety of factors, including our hormone balance.

BMR Variables

Muscle Mass – Aerobic exercise such as running or cycling has no effect on BMR. However, anaerobic exercise, such as weight-lifting, indirectly leads to a higher BMR because it builds muscle mass, increasing resting energy consumption. The more muscle mass in the physical composition of an individual, the higher the BMR required to sustain their body at a certain level.

Age – The more elderly and limber an individual, the lower their BMR, or the lower the minimum caloric intake required to sustain the functioning of their organs at a certain level.

Genetics – Hereditary traits passed down from ancestors influence BMR.

Weather – Cold environments raise BMR because of the energy required to create a homeostatic body temperature. Likewise, too much external heat can raise BMR as the body expends energy to cool off internal organs. (BMR increases approximately 7% for every increase of 1.36 degrees Fahrenheit in the body's internal temperature).

Diet – Small, routinely dispersed meals increase BMR. On the other hand, starvation can reduce BMR by as much as 30%. (Similar to a phone that goes into power-saving mode during the last 5% of its battery, a human body will make sacrifices such as energy levels, moods, upkeep of bodily physique, and brain functions in order to more efficiently utilise what little caloric energy is being used to sustain it).

Pregnancy – Ensuring the livelihood of a separate fetus internally increases BMR. This is why pregnant women tend to eat more than usual. Also, menopause can increase or decrease BMR depending on hormonal changes.

Supplements – Certain supplements or drugs raise BMR, mostly to fuel weight loss. Caffeine is a common one.

  • Work & social stress can trigger hormones that can cause our bodies to prevent fat cells from releasing their contents, despite a calorie deficit (and actually convert muscle tissue to glucose instead).

No single value for Resting Metabolic Rate is appropriate for all adults. Adhering to the nearly universally accepted MET convention may lead to the overestimation of the RMR of approximately 10% for men and almost 15% for women and be as high as 20%–30% for some demographic and anthropometric combinations”.

  • Our bodies can down-regulate some functions to conserve energy and reduce BMR significantly if we eat too little.

The basal metabolic rate, which is the amount of calories required by the body at rest, is determined by two hormones produced by the thyroid gland: thyroxine, also known as tetraiodothyronine or T4, and triiodothyronine, also known as T3.

T3 and T4 release from the thyroid gland are stimulated by thyroid-stimulating hormone (TSH), which is produced by the anterior pituitary. These hormones affect nearly every cell in the body except for the adult brain, uterus, testes, blood cells, and spleen. They are transported across the plasma membrane of target cells where they bind to receptors on the mitochondria, resulting in increased ATP production. In the nucleus, T3 and T4 activate genes involved in energy production and glucose oxidation. This results in increased rates of metabolism and body heat production. This is known as the hormone’s calorigenic effect.

Disorders can arise from both the underproduction and overproduction of thyroid hormones. Hypothyroidism, underproduction of the thyroid hormones, can cause a low metabolic rate leading to weight gain, sensitivity to cold, and reduced mental activity, among other symptoms. In children, hypothyroidism can cause cretinism, which can lead to mental retardation and growth defects. Hyperthyroidism, the overproduction of thyroid hormones, can lead to an increased metabolic rate, which may cause weight loss, excess heat production, sweating, and an increased heart rate.

An abnormal basal metabolic rate is not necessarily indicative of disease; a number of physiological factors can alter the BMR by influencing cellular metabolic activity. For instance, males are more likely than females to have a high BMR, and in women, the BMR may rise to abnormal levels during pregnancy or lactation. An individual's BMR varies greatly with age: infants and children typically have a high BMR, required for growth, while the elderly have a low BMR. Tall, thin people have a higher BMR than their shorter counterparts, even with the same weight, due to the greater surface area of their skin. The metabolic rate also decreases during sleep and increases in exercise, and individuals who exercise regularly have a higher BMR than those who are sedentary. Environmental temperature also has an effect: the BMR is increased in both heat and cold.

  • Poor sleep can create stress hormones that prevent fat loss.

  • What you eat matters. High glycemic foods cause insulin secretion that will prevent fat stores from releasing their contents. (Even if you are on a calorie deficit) and if you eat more regularly the cells will stay shut.

The reality is there are a number for factors which govern whether your body will allow your fat cells to release energy and they are hormonal.

If you hormone balance is not working well, you will struggle to lose weight. If it is working well, then you will be very likely to reach a healthy weight and body composition without hunger and without measuring all your macro’s constantly (like our ancestors did for the last 300,000 years before the invention of Tupperware).

Incidentally…at the end of the J8 Challenge after all the weighing and measuring food, and macro-nutrients, I decided to go back onto a ketogenic diet that I had enjoyed a couple of years before.

I found that it gave me more energy, prevented me from feeling hungry throughout the day and that I thrived on it.

Ketogenic diets are great for those wishing to lower inflammation caused by high-glycemic foods , which is why they are recommended for those with heart disease and for those that want to avoid plant sterols and omega 3/6 fatty acid imbalances.

They are also fantastic for generating the perfect environment for hormones to thrive.

After 10 days of eating mainly fats, fish and meat, with less exercise than when I was on the J8 Challenge and without the need to measure my food or macro’s at all……I lost 9 lbs.

Now….a year later, I eat a mainly ketogenic diet, for it’s heart-healthy low-inflammation benefits for my heart health, and I am the same weight.

PT’s these days are obsessed with trying to get people to “stick” to their eating patterns, and out of laziness their suggestion is often to allow regular indulgences of “foods” that really don’t help with hormone balance and are nutrient poor.

Ironically these are the foods that actually trigger the difficulty in sticking to the diets in the first place as they trigger insulin, store fat and increase hunger...leaving the tell-tale “hangry” feeling when insulin is not regulated properly. Add in processed foods and vegetable oils and you start to spark a little insulin resistance which is going to destroy your chances of actually losing weight or becoming healthy long-term.

And all this while your PT would have you painstakingly measure every nutrient out on miniature scales and store it in Tupperware for the day, and feel starving!

How did we cope before scales and Tupperware?

The next time you have a PT tell you “calories in v calories out!”…….get a new PT!

It doesn’t work that way in practice, and you should find someone prepared to work more closely with you to understand what your bodies needs, and how you respond to training and diet in the context of everything else in your life and environment.

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