Mythbusting diets

Finding the optimal diet for you

Mythbusting diets

At the Cheltenham Science Festival at home 2020, geneticist Dr Giles Yeo (Cambridge) and Professor Tim Spector (Kings College London) spoke in a talk called Personalised Diets about how a more personalised approach to what we eat is needed and how a ‘one-size-fits-all’ approach doesn’t work.

The talk is on the Cheltenham Festival’s YouTube page and is available for 30 days after airing.


I am by no means an expert on this subject matter. What I have learnt about this topic is from the Cheltenham Science Festival 2020 talk. This post is a summary of those findings.

Genetics & obestity

Not quite in line with the article’s title, but let’s take a quick detour into the relationship between genetics and obesity.

We used to think that body weight was composed of what and how much we eat and how much exercise we get so that we can burn off some calories. From a physics perspective, that’s true, but genetics can also affect some people’s level of restraint when it comes to food. If someone, by virtue of their genes, is, say, 3% less likely to say no when faced with whether they should eat something unhealthy, this could result in them eating it. These small micro-decisions build up over time and can ultimately affect a person’s body weight.

Myth 1: every adult the same amount of calories

You may have come across the magic number of 2000 or 2500 as the amount of calories we need to consume daily. Those figures came from studies conducted 30 years ago on a small sample size, and have not been updated since. Unfortunately, as in the case of Professor Spector, this was also taught at some medical schools as the ground truth.

Dangers of marketing on food labels

On food packets, we often see nutritional information, such as the percentage of fat, sugar and salt. However, concerning whether a particular item of food is healthy, this may not be as useful a guide as you may initially think. The problem is that the food manufacturers can market a product as ‘low fat’, for example, by adding in fake soy, or some other ingredient, to shift the ratios in their favour. An item that had previously 30% fat, say, may now constitute only 5%.

Myth 2: it’s low on calories so it must be healthy

Put simply: it isn’t just about calories.

Another potential problem is here that someone might eat more of a ‘low calorie’ marketed item simply because they think it is healthy.

Thirdly, there’s a fair margin of error here. According to Professor Spector, the amount of calories recorded on a packet is +/- 20% – quite a high margin!

What can you do then to follow a healthy diet?

  1. Limit the number of processed foods. This may sound obvious, but it may be less clear that processed food isn’t necessarily bad.
  2. Limit snacking. Healthy snacks between meals, such as fruit, is probably OK. Where possible, try to limit snacking. According to Professor Spector, the average person eats six times a day. Yet, leaving large fasting intervals could be beneficial for your metabolism.
  3. Find out what works for you. Eat for your microbiome. One resource on some tips on how to do this is an article in the BBC Science Focus magazine by none other than Professor Spector himself.

Efficacy of vitamins

This section may be somewhat controversial, so please be aware that statements of fact in this section should be attributed to Professor Spector, not me.

According to Professor Spector, studies in the last five to ten years about whether vitamin D, in particular, does help to prevent osteoporosis have been negative. He said that there seems to be no benefit and that while there is an association, it is not causal. The same also applies to other vitamins, such as vitamin C, fish oil and others. With a large trial, such as the ones in the US, there seems to have been no effect on the supplements.

The UK government often encourages people to get vitamin D, the sunshine vitamin, because of the association studies. There appears to be no evidence to show that it does prevent fracture of any bone loss. The vitamin industry supports a lot of research, so we have to be wary of studies purporting the benefits if there’s a vested interest. Vitamin D and fish oils, two of the most popular vitamins, are purchased by many, and the vitamin industry may well be a billion-dollar con.

I’m not in a position to be offering medical advice; I’m only summarising the findings from the talk. I would urge you to conduct your own research on this matter before making up your mind. Personally, from a quick look, I have found mixed conclusions.

Giles Yeo has also supported the claims on vitamins (see everything above in this section) being potentially useless. From a Horizon documentary he did, Yeo found that vitamins are considered to be food, not drugs. Consequently, they’re not regulated in the same rigorous way that drugs are, such as paracetamol. In the case of paracetamol, there have been clinical trials to show that it can reduce fevers, but no studies are needed to show that vitamins are provably useful because they’re considered food. If you’re doubtful of this, read the food PDF put out by the UK government that states that vitamins are regulated as food.

Is breakfast necessarily the most important meal of the day?

The notion that breakfast is important seems to be grounded in the view that skipping breakfast worsens our metabolism and it’ll make us hungrier, so we’ll eat more and put on more weight.

In the opinion section of the British Medical Journal, Professor Spector writes about how eating breakfast is put forward by food companies as being very important. Professor Spector said this myth was debunked by 11 randomised trials published in the British Medical Journal. I haven’t read the paper in full, but the conclusion casts doubt on whether eating breakfast is an effective technique for weight loss and calls for ‘further randomised controlled trials of high quality’. From this alone, it seems that the conclusion isn’t that the myth has been debunked but that there is doubt about whether breakfast can help with weight loss.

There’s a lot more information on this, from both those in favour and those against skipping breakfast. What I took away from this is that it depends (which is why this section includes the word ‘necessarily’). In line with the rest of this piece, there isn’t a right answer for everyone.

Photo by Hermes Rivera on Unsplash