Doctor Tim Spector: The shocking truth about weight loss, calories & diets

Tim Spector - Calories are a total lie

Did you listen to Steven Bartlett’s ‘Diary of a CEO’ podcast with special guest Tim Spector? In the episode, the British epidemiologist, medical doctor and science writer behind the new diet app ‘Zoe’ said:

  • The key to good health is focusing on your gut health
  • Ultra-processed foods are ruining our health
  • Calorie counting is ‘complete nonsense’
  • Exercise won’t get you closer to your weight loss goals

It’s fair to say that the podcast has received a fair bit of backlash. Fitness experts have branded Tim Spector as ‘irresponsible’ and ‘amateur’, claiming he shouldn’t deny the simple science of ‘calories in, calories out’.

But what did we think here at Purition HQ? Well, we’re over the moon that Tim Spector’s research finally proves what we’ve been saying and promoting for the last 10 years:

Eating more whole foods, more variety of foods, fewer processed foods, less sugar – and maybe even a bit of fasting here and there – is key to long-term health and weight management.

In case you don’t want to listen to the full, hour-long podcast (linked at the bottom of this blog post), here’s a run-through of the key points discussed. And, in line with Tim Spector's research, how Purition can help you to eat yourself healthy from the inside out!

1. Gut health is key to good health

Spector describes the gut microbiome as “A community of microscopic bugs in our intestines. It’s called a biome because it’s like a jungle community. Lots of different species co-exist together – thousands of them!”

He explains that all of these microbes pump out chemicals that are vital for your immune system, which helps to fight ageing, cancer, covid, allergies and more. Amazingly, he claims that some microbe chemicals even affect the brain and make the difference between whether you feel happy or sad.

But how much of a role do your gut bug plays in your weight? Well, a big one: “Your gut bugs are key to regulating how much you eat, your appetite and when you feel full.”

How to support your gut microbiome

We hear you. If gut bugs are key to good health, how can you support yours?

Spector explains that “You have to eat a more diverse range of plants. We did a study a few years ago and discovered that if you can get up to 30 different plants per week, you maximise the diversity of species in your gut.”

Eating 30 different plants per week might seem like a lot, but it’s not just vegetables. It’s nuts, it’s seeds, it’s fruits, it’s herbs, it’s spices – even coffee.

The good news? By enjoying Purition daily, you’ll instantly bump up your plant numbers by 10–14. Made with flax, chia, pumpkin, sesame and sunflower seeds, almonds, coconut and more, Purition is a daily feast for your gut.

Spector also recommends eating more fermented foods (think kimchi, sauerkraut and kombucha), as well as reducing how many ultra-processed foods you eat: “All the groups in the population that have the best gut microbes don’t eat ultra-processed foods”.

2. Calorie counting is 'nonsense'

You might’ve already read our blog on calorie counting and why it doesn’t work for long-term weight management – and Spector’s research completely backs up our approach.

“It’s complete nonsense” claimed Spector. “There’s never been any long-term study showing that calorie counting is an effective way to lose weight or maintain weight loss after the first few weeks.”

He goes on to explain that while strict calorie counting will help you to lose some weight, it’s not sustainable. Even if you’re successful, your body’s evolutionary mechanisms will make you hungrier and hungrier every week that goes by on a low-calorie diet.

“Your body will go into shut-down mode, your metabolism slows down and, inevitably, more than 95% of people will go back to their baseline weight. Many go above it."

What's the alternative to calorie counting?

Deleting your calorie counting app and focusing on diet quality instead.

Spector gave an American experiment as an example. In the study, they gave people identical meals for 2 weeks – identical calories, identical macros. The only difference? One was homemade, the other was ultra-processed.

“The group with the ultra-processed meal overate by about 200 calories every single day. They kept coming back to the buffet for more. So even though they ate the same calories, the effect of ultra-processed foods on the body meant that they were hungrier.”

So try to start eating more nutrient-dense whole foods – think unprocessed meat, fish, full-fat dairy and non-starchy vegetables. Getting started could be as simple as:

3. Time-restricted can help with weight loss

Time-restricted eating simply means changing your eating window. Typically, most people in the UK and the US eat for around 14–16 hours a day. 

But Spector explains “In time-restricted eating, we try to reduce that to something like 10 hours, on average. For example, you might start eating at 11 am and finish eating at 9 am. Or 8 am until 6 pm.

There are plenty of studies showing that it helps with energy, weight loss, inflammation levels and mood. The science is really interesting, but simply, your body needs time to recover. If you rest your gut for 14 hours, you give time for all the microbes to come out and act as a repair team that hoover up all the mess you’ve left behind.”

He goes on to say that although he’s seen great benefits from time-restricted eating, it’s not right for everyone. If you’re interested, give it a try, test out different eating windows and see if it positively impacts your energy and hunger levels.

Tim Spector/ Diary of a CEO - Calories are a total lie

4. Exercise doesn't impact weight loss

Regular exercise has many health benefits beyond weight loss. It reduces your risk of chronic conditions, improves your mood, sleep quality and self-esteem and even helps to maintain your joints and muscles.

But Spector points out that exercise isn’t the key to weight loss.

“Exercise has very little role in weight loss. All the long-term studies show it doesn’t help weight loss. It’s been grossly exaggerated as an easy fix for the obesity problem. On its own, if you don’t change your diet, it’s of no use.”

He goes on to explain that exercise makes you build up hunger. After exercise, your metabolism slows down and your body tries to regain the energy (i.e. calories, from food) that was lost.

If exercise isn’t helpful for weight loss, what is?

If your goal is weight loss, your priority should be changing your diet. And, as we said earlier, that means eating more whole foods and fewer ultra-processed foods.

Whole foods work in synergy with your hunger/satiety hormones, gut microbiome and other systems that help you to regulate your body weight, naturally.

It can be helpful to change one meal at a time, rather than overhauling your entire diet at once. Why not start by having Purition for breakfast? It’s a small change that means 33% of your diet will come from whole foods!

5. Coffee has health benefits

Many of us consider coffee a guilty pleasure, but according to Spector, it's actually a healthy habit.

The Zoe blog explains that coffee may protect against heart health. For instance, one large study concluded that coffee consumption was associated with a long-term lower risk of developing heart failure. 

And according to a review, drinking 3–5 cups a day is linked to a 15% reduction in cardiovascular disease, compared with drinking none – in Spector's words, "If you drink 3 cups of coffee a day, studies show that you're less likely to die ten years later."

How can I ensure my coffee habit is healthy?

The key to coffee (and caffeine) is in the dose.

"There is variability. Some people get the shakes, can't sleep and experience other side-effects if they have too much. But if you get the dose right, coffee can be very beneficial for you."

Spector also claimed that "Studies show that people who drink decaf coffee also experience similar heart health benefits. Green tea is also pretty good."

Ultimately, everyone's different, but it's best to drink no more than 3 cups per day – and try to stop before 2pm to avoid sleep disruptions. And if you find that you're sensitive to caffeine, why not follow Spector's tips and give decaf coffee or green tea a try instead?

Listen to the full podcast here:

We hope you found this information useful! We'd love to hear what you thought about the Tim Spector & Steven Bartlett podcast. Drop us an email on with your thoughts!


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