If 3500kcal deficit = 1lb weight loss, why doesn't it work?

[Watchkeys]

I'm just curious to know what people think about this. Lots of people on here are sticking to a deficit. It might not be 500kcal per day, but some increment of that would incur some increment of weight loss, if the theory holds. Millions of people are on kcal controlled diets, and mostly, they don't work, especially not long term.

What's going on?

If we can have different metabolisms, then 1kcal will = a different amount of fat per person.

No it won't. 1lb is 3500 kcal and that's it. There are three reasons diets don't work:

1. People under estimate calories in.
2. People over estimate calories out (most women need much less than 2000 calories to maintain)
3. Once the weight is lost people stop dieting and go back to their old eating patterns - the ones that made them heavy.

There's no secret, whatever anyone says. 5:2, keto whatever - they all work by restricting calories.

And I say that as a fellow fatty!

Because human beings aren't in a closed system, and aren't bomb calorimeters.

6 weeks? To get to Level 4?

Have a look on PubMed. There’s loads.

Maybe also follow some well educated PTs like Emma Storey-Gordon (Sports Science degree, evidence based, well researched and quotes sources), Ben Carpenter. Nutritionists like Graeme Tomlinson at thefitnesschef_. Maybe also find some body builders at your gym who are getting ready to compete and ask them about calorie counting and nutrition.

Yes and some of their female clients who had previously restricted calories had lost their periods despite still not losing much fat, all that fat available for the body to burn for fuel but instead it turns off the periods, which kind of shows how the fat isn't really available for the body to burn in some people due to whatever is going on in their body.

Once they start fuelling themselves properly their periods come back and they gain muscle and energy etc. and they get on a far healthier path.

I think a lot of people don't understand TDEE - I didn't for many years and stupidly believed that 2000 calories was what I needed in a day despite being 5'2 and relatively sedentary.

My actual TDEE is lower. To lose a lb a week as promoted by many diets I would need to stick to around 1100 calories which isn't sustainable for me. Since doing the actual maths and deciding to lose weight slowly, I've been more successful by increasing exercise and sticking to 1200 calories Mon-Fri and 1700 at weekends.

Another important factor that I was slow waking up to, is that your percentage of body fat affects your metabolism I've lost just over a stone, 9 % of my body weight but about half my body fat and my TDEE has actually gone up by about 50 calories a day.

I'm into the last half stone - and yes it's hard, but understanding my actual calorie requirements means I'm more realistic about it sticking to my limits and hitting my goals at a steady pace.

@Irritateandunreasonable
Would you say that the difference is that everyone needs a different amount to be in a deficit tho? I know many skinny people who can eat 3k cals daily and not gain, and will lose in 2.5k, without exercise. Others gain on 2k and can't lose on 1.5k
So we need an individualised way to work out people's actual TDEE, not using a generic calculator. Then their own amount to create the deficits.

The only way to do that is by accurate tracking over a period of time.

@PortiaWithNoBreaks

Have a look on PubMed. There’s loads

Can you recommend any specifics? You really sound like you know what you're talking about.

I'm a PT, Level 3, yes, 6 weeks of training. It's really not a biology degree. My knowledge comes from successfully helping clients lose weight, and from reading and breaking down scientific studies and articles, but you've clearly found a study that proves that a 3500kcal deficit actually does consistently cause a 1lb loss of fat. I'd love to see it. I didn't know it existed. Could you provide a reference? The NHS don't even know where it comes from. They'd be really interested, since they base so much on it!

It does work. People just often don't stick to it.

I didn't know it existed.

It does, it's just from 1958 and has long been replaced with more statistically accurate models that account for metabolic adaptation. The NHS is probably aware that Wishnofsky is the basis for their guidance, though. It's hardly lost to the mists of time.

equally google scholar. there are even a few recent articles dated 2023 about calorie deficit and obesity
however you need to pay to see beyond the abstract.
hunt specifically for those written up by university research teams.
found a very dated one that did the math and came up with 3,511 ;)
either way calorie deficits work.
the 2023 article suggested the fast 800 diet as unhealthy although i believe that is long term, from my research a few years ago it was suggested that for healthy individuals who's obesity causes no metabolic issues loosing weight faster is better due to a decrease in joint injury as well as a decrease in yet to be diagnosed cardiovascular changes.

One thing to consider if you are wondering why your clients can't lose weight, is are they telling you an accurate story. I admit I've had my weight monitored by a PT, and told them I was sticking to the diet, when I wasn't. Add to that genuine mistakes (not knowing how many calories a food has), forgetting (not logging a biscuit at work or milk in tea), misconceptions (thinking exercise burns lots of calories), how would you ever know what someone has eaten unless it's laboratory conditions.

You even see it on here, an OP says "I'm sticking to x calories and can't lose weight", then list what they've eaten, and it's obvious without even looking it up the calorie count is way over that.

I think it is relevant in that if a human loses a pound in weight then a human has burnt 3500 Kcalories, which have not been replaced.
You keep saying it’s more complicated, but who said it was simple?
The factors that influence weight loss don’t affect the calorific value of fat so I don’t understand why it is this particular fact that you keep objecting to.

@WhatWouldJeevesDo

The factors that influence weight loss don’t affect the calorific value of fat so I don’t understand why it is this particular fact that you keep objecting to

Because we are told that if we eat 3500kcal less, we will lose a lb of fat. There are plenty of people (including on plenty of threads here) who are counting their calories to the digit, to try to adhere to this, when, as you say, there are many other factors that influence weight loss.

@FrozenGhost

My clients do lose weight. I'm not looking for advice on how to do my job better. I'm on the kcal counting board, asking why people adhere to '3500kcal deficit = 1lb fat loss', when it generally doesn't work, and other approaches fare much better, and I see it week in and week out.

For me to lose a pound a week to achieve my goal I need to commit to 4 workouts and daily calories at around 1450. The 3500kcal is the weekly reduction in your intake to lose a pound.

I weigh everything, count every it of oil, sauces etc etc. Most folks don't count calories correctly and are not tracking everything. I have lost two and a half stone y simply tracking everything and committing to my goals. I know when I go off track and bring myself back on line.

Because we are told that if we eat 3500kcal less, we will lose a lb of fat

Only if you eat 3500 less than you need for maintenance. People eat too much, that's why they need to diet.

If you need 1500 calories for maintenance, but eat 2500 you will put on weight. Reducing that 2500 to 2000 (ie 3500 a week) won't make you lose a lb of fat because you're still over eating.

Most people underestimate (this is well researched and proven)

The NHS didn't mention Wishnofsky, whose 1958 article stated that fat holds 9.5kcal per gram (not the 9.0kcal that the NHS state) i.e. 3752kcal per lb. If they are using 3500kcal with this as their basis, why have they changed the figure, and why don't they tell us that's where it's based?

Do the accurate models accounting for metabolism accept that everybody's metabolism is different, or use an average metabolism? Do they account for the vastly different metabolism of the macronutrients? This is my point exactly: people who adhere to trying to lose 1lb of fat by eating 3500kcal might as well be saying that everybody is the same height, and we can all run at the same speed for the same amount of time. Averages are useful on a societal level, when looking at trends. They are not useful when applied to an individual.

So, various PPs are saying that we're fat because we can't count, or we lie.

Why do you think this started happening in the late 70s/early 80s, when less than 3% of us had an issue with our weight before that? Why would you say it started specifically then?

'm on the kcal counting board, asking why people adhere to '3500kcal deficit = 1lb fat loss', when it generally doesn't work, and other approaches fare much better, and I see it week in and week out.

Plenty of people on here telling you it DOES work. Unless you are personally monitoring everything eaten by those who tell you it doesn't work to ensure they are measuring correctly, and recording absolutely everything they eat and drink, you cannot possibly say for sure that it doesn't work.

@titchy

People eat too much, that's why they need to diet

But there are people listing their 1000kcal per day diet who feel shit and are still not losing weight, so your argument falls.

OP you obviously desperately want to share your method so why don’t you just do that. But be aware doesn’t allow business advertising. With respect you are a PT with, as you say, 6 weeks training and a small client base. The reason why people don’t loose weight are many and complex, and just not calorie counting and using whatever method you like to use isn’t going to be what solves the global obesity crisis.

Why do you think this started happening in the late 70s/early 80s, when less than 3% of us had an issue with our weight before that? Why would you say it started specifically then?
Increase in use of processed ready meals, more take aways, price of alcohol relatively cheaper than previously, Increase in car ownership so fewer people walking etc etc

Well then they're eating more than 1000 a day and calculating wrong, 'forgetting' things, saying 'oh well fruit doesn't count' etc. Which most people do.