We cannot survive on fats or plants alone- the reality check behind keto and vegan diets

Laurentia (Laura)Campbell
9 min readJul 12, 2021


As someone who has studied neuroscience, nutrition and had a severe eating disorder (I am now an expert in health and total foodie), that nearly killed me in 2017 and has left me brittle boned, I HATE DIETS. They drive me mental. They make no LOGICAL SENSE. We cannot have a one size fits all, magical solution to our health and weight. Every single person’s genes, metabolism, age, height, activity level, taste buds, immune system, amount of sleep, neurotransmitters and gut microbiota differs. Each person has a different set of emotions, habits, food availability and accessibility and budget, and so selling a “eat this and it will save all your problems” diet is ludicrous. First, it was fat-free everything, now with ketogenic diets it’s all fat and carb-free and we have plant-based diets, intermittent fasting and god knows what else. When are we going to stop demonising food and making ourselves feel guilty for satisfying a basic biological need and eating? Each body responds to fats, carbs and activity in a personalised way. Food is medicine and medicine needs to be personalised.

However, most importantly, we need to stop food morality. There is no good and evil foods. CARBS ARE NOT THE ENEMY (Holesh, Aslam and Martin, 2020). Ketogenic diets that restrict what you eat by encouraging completely cutting out carbs like cereals and bread are silly. We have a big insulin dip first thing in the morning. Insulin controls blood sugar, and low blood sugar makes you hungry. Skipping breakfast denies your body and brain the vital nutrition it needs first thing in the morning, making you more likely to binge eat later on in the day, and less likely to be at peak performance. When your blood sugar is low, the best thing for it is carbohydrates as these are quickly released into the blood. However, it depends on the type of carbohydrate. You have your glucose and fructose and galactose simple sugars which add together to make lactose (the sugar in milk) and sucrose (the sugar in fruit) and starch (the complex sugar in fruit and veg) and glycogen (the complex storage sugar in humans). The more complex a sugar, the longer it takes to be broken down (metabolised- this is what metabolism is, the chemical reactions in the body) and so the longer your energy (we use fats, carbohydrates and proteins in a process called respiration which gives us energy) levels stay high. It is energy dips from high simple sugar (glucose, syrups, fructose, agave nectar, honey, molasses etc) foods that make us hungry as our bodies and brains need more energy (Ferretti and Mariani, 2017). Ludwig (Ludwig et al, 2018) and team found that if you have too much simple sugar, it causes low energy, as it causes a massive energy high which our bodies respond to with more insulin, causing a massive energy low. Carbohydrates are not the enemy. Yes having too many carbohydrates can cause insulin resistance, diabetes type 2 and obesity which hugely reduce life expectancy and quality of life, however, the answer is not to skip them out completely. Our brains and bodies need them for fuel. However, what is important is the type of carbohydrate and making sure you are not having too much all at once. Cereals and bread are not enemies, just watch the sugar content. Making something off-limits makes you crave it more and if you restrict something, you are more likely to binge on it. Make nothing off limits and suddenly you will find you don’t crave anything. Eat your breakfast and enjoy your bread at mealtimes, up a table and enjoy it. GUILT-FREE.

On that same subject, FATS ARE NOT THE ENEMY. There are no “good” and “bad” fats. We actually need ALL TYPES OF FAT. Unsaturated fats, such as monounsaturated fats found in nuts and seeds and omega-3 polyunsaturated fats found in fish and seeds like flax seeds, help to increase HDL levels. HDL takes cholesterol from the tissues to the liver where it is broken down, so it lowers blood cholesterol and lowers your chance of heart disease. LDL cholesterol (found in animal fats, coconut and plant based oils and trans fats found in processed foods), moves cholesterol from the liver to tissues and therefore has been labelled “bad” as it increases the chance of heart disease and diabetes. However, LDL cholesterol has multi-functions. It also is the basis of sex hormones like Oestrogen (which is why Cholesterol levels increase in menopause and why high cholesterol is often found in anorexia- as the cholesterol is not being converted to oestrogen) and Testosterone and of neurotransmitters like Serotonin, which is our happiness brain chemical. Many vital vitamins and minerals are also fat-soluble, and therefore without these “bad” fats, we can get severely malnourished. In the absence of sufficient carbohydrates, we use fats and proteins to make energy instead. Breaking down complex molecules into smaller ones (for example breaking down food into smaller molecules like proteins, carbohydrates and fats to give off energy) is called catabolism, processes that build molecules are called anabolism (for example grouping together simple sugars like glucose to store them as glycogen or fat if we have too much sugar in our bloodstream). Both carbohydrates, fats and proteins are used to make energy. Cut out fat and you can’t make cell membranes, collagen for your skin (which keeps you looking young) and for your joints, and you can’t make oestrogen and testosterone and so put yourself at risk of osteoporosis and infertility. Trust me. I was encouraged by doctors (as we have a family gene that puts us at high risk of heart disease) to only eat “healthy fats” and now am suffering the side effects. Fat is not bad. Fat is good. However, eating only fats means that you are not getting enough carbohydrates for energy, put yourself at risk of high cholesterol, and also keto diets are often low fibre, which increases constipation, kidney stones and is bad for your gut microbiota. Fats are not bad or good, everything in moderation.

PLANT BASED DIETS ARE ALSO NOT THE SOLUTION. Yes, reducing meat and fish and dairy is good for the environment. Yes, consuming a diet high in red meat is sub-optimal, as it is high in saturated fats and bad for the planet, yes we do over-fish and we are destroying the ocean ecosystem, yes some people are dairy intolerant, but meat and fish are an essential part of our diet. We can get protein from plants, yes and we can get some iron mineral (needed for energy) from plants too, but there are some essential amino acids, that you can only get from animals and fish. We need omega-3s (Cholewski, M, 2018) for our brain, and we can only get DHA omega-3 from animals and plants. Plant-based sources of omega-3, like flax-seeds, contain (Ede, E, 2020) only ALA omega-3 and without DHA (Dyall, S, 2019) we cannot make vital parts of our brain, like synapses and myelin and mitochondria (which makes energy) and some neurotransmitters, impacting our mental health. A plant-based diet often includes more FIBRE which is amazing as it helps to decrease LDL cholesterol and also helps feed our gut microbiota. As our gut microbiota helps boost our mood (via the brain-gut axis where it increases Serotonin), a high fibre diet has lots of benefits for health. Most plant-based diets are low-fat yes, but make up for this by being very high carbohydrate. More fibre is good for mental health. More dietary veg (high in magnesium, A, B, C, D, E and K vitamins which give us energy and improves our vitality and strengthens our immune systems) is a definite physical and mental health hell-yeah, but we need that DHA too. We should definitely eat a MORE plant-based diet, but not ONLY plants.

HIGH PROTEIN IS NOT EVERYTHING. Yes, protein is good. It helps (like fat) (Santos-Hernandez, et al. 2018), keep you feeling fuller for longer, so you are less likely to snack and over-eat. However, buying specific “protein” foods is just buying the marketing. The best sources of protein? Broccoli, peas, fish, meat, eggs, chickpeas, lentils, tofu, dairy products, beans and there is even some protein in a simple 17p potato. Protein is an essential part of diet, but not everything and so don’t let yourself get conned by the food advertising. You need carbs and fats and vitamins and minerals and fibre too!

Figure 1: Biological sources, pathways and processes for energy synthesis. Biology online.

At the end of the day, you need to eat what your body needs for its nutritional requirements. This is about eating what we require MEDICALLY (body and mind) and METABOLICALLY (how much energy you need based on your activity level, age etc). We are, thanks to organisations like Zoe and Second Nature and Oviva, heading to a more personalised technological approach for balanced and sustainable nutrition and health and weight. Until a time when we are at the point where we can tailor nutrition to an individual based upon their blood test results (medical evidence), we need to stop self-experimentation and listen to our bodies. It is about being very active with three nutritious meals (eaten slowly and mindfully, around a table) a day (no skipping breakfast and bingeing at night) with all food groups, lots of plants and watching the sugar and as unprocessed as you can be. It’s not complicated and there are no magic fixes. It’s about doing the same thing over and over each day and ENJOYING your meals. NO BRAINER!



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Laurentia (Laura)Campbell

Neuroscience, mental health and nutrition academic and writer. Life-experimenter, trying to add value with an insatiable appetite for actioning positive change.