Do you need to eat more to lose weight?

Thanks to the position I find myself in I get asked a lot of questions about nutrition and fat loss every day. I absolutely don’t mind this and consider it an honour – it’s pretty cool to be the go-to nutrition person – but at the same time there are some questions that annoy me a bit. Not, I want to stress, because the person has asked, but because their asking implies something:

  • If a person asks if they need to eat more to gain weight, that means they think they probably do
  • If they think they do, that means that someone has told them that it’s possible to eat too little to lose weight
  • This means that this person has been told that your metabolism has some kind of starvation mode or another tomfoolery which prevents weight loss if calories are too low
  • That is a lie

So in this blog, I’d like to expand upon what’s going on here: what the common beliefs are, and why this myth came about. If my conversations with coaches and non-coaches alike are anything to go by, a LOT of you have been lied to.

The Lie

There are a lot of different versions of this lie, with two primary trends dominating, and with one of these being a bit more complicated than the other. The first version claims that when your calorie intake gets too low (wherever the cut off for that is…) your body enters ‘starvation mode’ in which it ‘holds on to body fat’ so as to protect you from starving to death.

This doesn’t make any sense at all, and literally defies physics. In physics the law of conservation of energy states that within a closed system energy can’t be created or destroyed, it can only be converted from one form into another. Looking back to the blog I wrote here on how fat loss works, you can see that body fat is a storage site for energy, which is utilised by your body when your intake is less than your expenditure. Simply, every day you use a certain amount of energy to do stuff, and if you eat less energy from that, physics states that the energy needs to come from somewhere.

If your body entered ‘starvation mode’ when your calorie intake was REALLY low, meaning that your body no longer used body fat stores, that would require the spontaneous creation of usable energy out of nowhere which is impossible. This one just isn’t true – but what about the second version?

The second version of the lie is that during fat loss your body adapts to the calorie intake you have been consuming, meaning that you need to eat progressively lower calories to keep making progress. After a while, folk claim, your body has adapted to SUCH low calories that you need to start eating more to ‘reset’ it. As a further branch to this, proponents of this idea will state that you should start a diet with as many calories as possible because when you start really low, your body will adapt to it and ‘where do you go from there’?

This one isn’t so much a lie but a myth, because while being fundamentally wrong, it’s based on some truth (albeit a misunderstanding of it). There isn’t space here to fully explore this concept, but the brief rundown of where this myth came from is the following:

  • When you lose weight you lose tissue, including fat, a little muscle, and a little organ mass (that’s normal, despite sounding pretty bad!)
  • Because of this lost mass, you burn fewer calories. A 140lbs person uses fewer kcals than a 180lbs person, and so after a successful diet you will require fewer calories to maintain your bodyweight than you did before
  • In some (but not all) research, some (but not all) individuals show a reduced calorie requirement after dieting that is larger than would be expected given the tissue loss that they have experienced
  • This doesn’t seem to be influenced by the size of your calorie deficit. It happens in some individuals in a bunch of different studies all with different dieting protocols – it may be that it just happens to some people for genetic reasons whenever they diet, but that’s a question that has yet to be properly answered
  • This is referred to as adaptive thermogenesis – this is your starvation mode or adaptation to dieting
  • The largest amount of adaptation seen in studies that aren’t explained by tissue reduction is 15%, and over 90% of this was because of factors I’ll discuss in a minute. On average it’s 3-7% or 60-140kcal for a typical 2000kcal person – not enough to halt weight loss, and again, most of that is explained by what I’ll look at in a minute
  • In other words, the adaptation to dieting is absolutely there for some people and scientifically interesting, but critically it’s NOT ACTUALLY CLINICALLY RELEVANT

So yes, your body does adapt to dieting. Your muscles get a little more efficient so they use fewer calories to do the same stuff, and your cells waste less energy as heat, but this only happens in some people when researched, it only happens in some studies (with no clear pattern, so it’s not clear that a larger calorie deficit makes it worse) and when it does happen it’s not that big.

So why is it, then, that some people can seemingly eat a tiny amount of food and never lose weight? And why is this sometimes fixed by eating a little more? Let’s look at the truth here…

The Truth

The most obvious issue here is that you’re eating more than you think. Those extra snacks you ate on Tuesday but didn’t think would matter, matter. That bite of cheese while cooking matters. The oil you cook in, the mayo on your sandwich, the extra bit spoon of PB, the latte – all of it matters, so if you’re tracking your food in any way be sure to include them. Research suggests that over 70% of people misreport their food intake (including dietitians!!) and the population most likely to do it by accident are those looking to lose weight. If you think you’re not losing fat despite being on low calories, spend a week tracking literally every morsel of food or sip of beverage on MyFitnessPal and see what happens….

Misreporting and eating more than you think isn’t a bad thing – it’s the norm, so please don’t read this paragraph as accusatory. It’s human nature to eat (we evolved a lot of drivers to do it!) and tracking food accurately is really, really tough. If you’re potentially struggling with this please do reach out to Rachael and enquire about coaching; fixing this issue is 90% of what coaching is and why coaching clients get results.

But let’s assume you’re adhering.

The first factor I’ll look at for why some people don’t lose fat on low calories is an extension of the point made above r.e. adaptive thermogenesis. As I mentioned there is up to a 15% reduction in calorie needs seen in people who diet, and some of that is because their body becomes more efficient. Most of it, however?

Up to 90% of the adaptation seen in people is because they MOVE LESS

During fat loss, some people experience a reduction in their sympathetic nervous system tone. In short, this means that people who are dieting get lethargic, tired, and less willing to move.

  • You won’t take that thing upstairs until you have to go up
  • Rather than walk a couple of minutes to the post box you’ll wait until you have to drive past that way anyway
  • You’ll fidget less, change position less when sitting, and generally burn fewer calories

All of this is subconscious, and with a little discipline you CAN overcome it, but if you’re not paying attention you might start burning fewer calories than you’d think and it’s nothing magic or highly scientific; you’re simply hungry and so less energetic.

This could mean that your usual 2000kcal requirement drops by 15% to 1700kcal, meaning that your small kcal deficit becomes maintenance. This is why moving when dieting (not necessarily exercising, but moving) is so important.

Next, there’s the water weight thing. Dieting, as far as your body is concerned, is a stressor, and stressors increase circulating levels of the stress hormone cortisol. Cortisol is a good and healthy thing (in chronic stress it can become a negative but that’s not most people and it’s beyond the scope of today, suffice it to say that cortisol isn’t bad and it doesn’t cause fat gain) but it does have cross affinity with other hormone receptors – namely aldosterone.

Aldosterone’s job is to cause your kidneys to reabsorb more water from your blood rather than diverting it to your bladder when you’re becoming dehydrated, and when cortisol binds to its receptors they ‘activate’. This means that stress, including dieting stress, causes you to store water.

You try to lose weight, your body stores water

This causes you to stay the same on the scales despite having actually lost fat because you’ve been in a calorie deficit

This causes you to get stressed, which stores more water

This causes more stress, which causes more water

This vicious circle can literally mask weight loss for weeks at a time, and so it’s really important to CHILL OUT when dieting. Stay hydrated, avoid acute massive intakes of salt, and spend some time relaxing – your mind, and the scales will reward you for it.

On the topic of water – women, stop using the scales to compare your weight week to week! Women can easily shift 10lbs in water weight over the course of their menstrual cycle, and this can mask fat loss very, very easily. If you’re using the scale to measure progress, track your cycle and compare week 1’s weight to week 1’s weight the following month, week 2 to week 2 and so on. This is the only way to tell if what you’re doing is actually working.

And then on the topic of using the scales – here’s the thing.

You may be progressing, but if you’re not using the scales properly you’ll miss it because your weight naturally fluctuates quite a bit during the day, and day to day. Here’s how to use scales if you are actually going to use them:

  1. Detach yourself emotionally from the number. The scales are a tool to determine if your actions over the last week/month have been congruent with weight loss, and so they are a method of judging your actions, and not yourself. If you can’t do this, don’t use the scales because it’s not worth it.
  2. Weigh regularly – research suggests that daily weighing leads to better weight loss progress and a better relationship with the scales because you can track fluctuations and understand them better. Take a weekly average of your daily weigh-ins (ignoring very high or low days) and use these to track progress
  3. Weigh in the morning, naked, after using the toilet and before consuming anything. If you weigh in clothes in the middle of the day you’re wasting your time because food and drink both have weight, and so if you’re eating a bunch of food, it’ll go up.

Weighing once per week or less is bad, if well-meaning advice. You have no way of knowing if you’re having a heavy or a light day that day because you have no other data, and so it becomes useless. Weigh more often and get good data, or don’t use this tool.

And finally, the last reason you may not see progress despite sticking to your diet is that fat loss takes TIME.

It’s not linear

It takes a good while

It’s hard to predict day to day because of the water weight issue noted above

If you are sticking to your diet and expecting dramatic results in a day or two, unfortunately, you will be disappointed and this isn’t because the diet isn’t working. If you are driving from one end of the country to the other and you’re not there after 20 minutes it’s not because the car isn’t working, and if you’re not lean after a couple of weeks it’s not because the diet isn’t working, it’s just that you need to be patient.

Some parting thoughts

Dieting on low calories has been shown in research to lead to better weight loss outcomes, better weight loss maintenance after achieving goals, and even less hunger and more motivation during the diet, but this won’t happen for everyone. For some, dieting on low calories is brilliant because it’s faster, easier (cheaper!) and extremely motivating because of the number on the scales and the way your clothes fit change pretty much week to week.

But for some it’s miserable. It means you can’t eat tasty foods you want to, some people get hungrier, your energy will be lower, and you might find it harder to concentrate at work or during other tasks. The rate at which you diet should be personalised to you, and that’s why coaching can be so useful.

But however you choose to do it, remember this:

Calorie deficits ALWAYS work. If you’re eating less energy than you use during the day you WILL lose fat.

If you don’t think you’re losing fat, look at the factors above – could one of them be hiding it, or holding you back?

And if the answer is no, you don’t need to eat more – you might need to eat a little less.

Thanks for reading!

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