Don’t be fooled by diets which promise dramatic weight loss by only eating steak and salads as the weight of the evidence leans towards these high-fat, low-carb diets being risky and potentially harmful to your health. This is based on the substantial body of highly-esteemed and independent scientific evidence from across the world. As such, the international scientific community, medical and dietetics associations, including the International Association for the Study of Obesity, all caution against high-fat, low-carb diets due to the associated adverse effects ranging from dehydration and electrolyte imbalance, to tissue (muscle, organ, etc.) breakdown, headaches, muscle weakness and cramps, diarrhoea and reduced exercise performance.
Common side-effects of a high-fat, low-carb diet
Let’s take a closer look at the side-effects commonly seen from following a high-fat, low-carb diet:
Weight loss and high-fat, low-carb diets
Scientists across the world have been studying the effects of low-carb, high-fat diets for years, for example the infamous Atkins diet and the South Beach diet. The Lancet, a highly respected medical journal made the following statement in 2004 about low-carb, high-fat diets:
“…the apparent paradox that ad-libitum intake of high fat foods produces weight loss might be due to severe restriction of carbohydrate depleting glycogen stores, leading to excretion of bound water, the ketogenic nature of the diet being appetite suppressing, the high-protein content being highly satiating and reducing spontaneous food intake, or limited food choices leading to decreased energy intake. Long term studies are needed to measure changes in nutritional status and body composition during the low-carb diet, and to assess fasting and postprandial cardiovascular risk factors and adverse effects. Without that information, low-carb diets cannot be recommended”.(1) Many of these long-term effects remain unclear.
Can a high-fat, low-carb produce weight loss?
Yes, a high-fat diet can produce weight loss – partly due to fat loss, but also due to substantial fluid loss (dehydration), low or empty bodily carb stores, as well as a loss of muscle mass (as it is used for energy). In addition, the total amount of calories you get in a day typically equates to a low amount (about 1200 calories) which for most people will result in weight loss.
Interestingly, when one looks at research comparing high-fat versus high-carb, low-fat diets, while the initial weight loss might be higher in a high-fat diet, after a 3-6 months the differences between diets are minimal.
The reality is, no matter what diet you are on – high fat, high sugar, “the beer” or ”cabbage-soup” diet – when you end up eating fewer calories than you need, you will lose weight regardless. The question is: How does that particular diet affect other aspects of your health beyond the weight loss?
High-protein diets and weight loss
Protein makes a meal more satiating (i.e. it makes you feel fuller for longer, similar to high fibre foods), it helps reduce loss of muscle mass and helps raise your metabolic rate, all of which could help with weight loss. So, does this mean high-fat, high-protein (and low carb) diets are the way to go? No, because there are negative side-effects to eating too much protein too…The crux here is how high? Again, I want to send a strong note of caution, as there are people who are at risk of developing or who already have certain medical conditions for which a high-protein diet is not recommended.
Dehydration and appetite suppression
Your body needs a critical amount of carbs to keep normal homeostasis and bodily functions going – many organs (the brain especially) are predominantly reliant on carbs. When you deprive your body of carbs, it leads to ketone production that circulates around via your blood stream. The more and longer you “carb-starve” your body, the higher the ketone levels. Ketones can suppress appetite, but of bigger concern is that they drop the acid-level (pH) of your blood, which at some point can result in keto-acidosis and a coma (a common concern in diabetics with poor blood glucose control). In an attempt to reduce ketone levels, your kidneys start working harder to excrete it via increased urine production, leading to dehydration and electrolyte imbalances.
The average person may not recognise the side-effects
For a health professional following a high-fat diet, it is perhaps easier to recognise and take pro-active, preventative action when side-effects occur. But for the average person it could be a major challenge to firstly, judge whether this diet is suited to their needs, circumstances, medical risk and conditions, and secondly, how to recognise and prevent severe side-effects.
In a carbohydrate-starved state, your body also produce various stress hormones, which can adverse effects such as suppressing your immune system. How does this affect your health and risk of disease in the long-run? Cancer? The ageing process? I don’t think we can say at this point in time. However, we do have substantial evidence on the positive effects of a well-balanced, calorie-controlled diet and active lifestyle.
Mental, physical and exercise performance
Losing several kilos can provide a big psychological boost and make you feel fantastic, confident and motivated. Even your exercise performance may improve because you weigh less, and therefore use less energy and effort to move about. (Every kilogram of weight loss makes weight-baring exercise substantially easier). The weight loss can also reduce blood pressure. These effects would be true of any weight loss achieved through whatever means. But the side-effects typically documented by the majority of people when they cut carbs is that it limits exercise capacity (intensity and duration), reduces muscle strength (and increases loss of muscle mass), increases cramping, reduces concentration, recovery and overall performance.
Nutritional status and health
Apart from the bad breath (due to the ketones), headaches, irritability, and lethargy typically noted by people on high-fat diets, there is also the potential for constipation (due to lack of dietary fibre – protein is not a source of fibre). Sufficient intake of fibre-rich food (wholegrains, fruit, veggies, legumes) is linked to the prevention of a range of diseases and cancers. So there are also questions around what this type of diet does to your gut health in the short to long-term.
The high intake of saturated (animal) fat associated with this type of diet and its link to negative health effects would also be of concern.
Do not exclude whole food groups
Each food group offers unique nutrients that are important to health and well-being, and it is for that very reason that decades of research have shown that a well-balanced diet is paramount for health, weight management as well as for exercise performance. Portion control (controlling your calorie intake) within each of the food groups is important, and should be related to your individual dietary needs and circumstances.
The inclusion of wholegrains, legumes, fruit and the full range of vegetables is a paramount component of a diet that supports health and longevity. Our bodies are perfectly capable of digesting, absorbing and using these foods to good effect. It has been the staple of many generations of healthy populations around the world and the indication is that it’s the exclusion of these types of foods that are linked to poor health rather than an inclusion thereof. Decreasing one’s intake of calorie-dense highly processed foods (including refined carbohydrates) is a good principle. Again, there is evidence that in small amounts there is room for these in a wholesome diet and lifestyle, and that including it would not be harmful to your waistline or health.
Some people do not fit the norm and may well feel good and perhaps even benefit from varying the fat, protein and carbohydrate proportions of the diet – whether to this degree remains to be proven. From the current research trends in “nutrition individuality”, it would be fair to say that these people are likely the exception rather than the norm. More research needs to be done before it can be conclusively determined that a highly specific diet or food will produce a specific outcome in an individual without affecting any other process.
What if you still want to try a high-fat, low-carb diet?
Due to the potential for minor to severe negative side-effects it would be best to do it under consent and strict supervision of a medical expert.
In my opinion, the safest and effective recipe for weight loss, improving insulin sensitivity, health, longevity and exercise performance:
- Everything in moderation…but a lot of activity!
- Find any type of activity you like – that gets the heart pumping – and do it as often as possible. Try something new every so often to keep things interesting!
- Eat fewer calories but don’t starve yourself to the extreme either. Include a variety of foods, in the right proportions instead of completely excluding any food group.
- Wholegrains, legumes, and a variety of fruit and veggies are healthy – the fresher and less processed, the better. There is room for a treat depending on how good the rest of your diet, physical activity routine and your health is.
- Go easy on your fat intake and focus on healthy fats such as mono- and polyunsaturated fat from vegetables oils like canola oil, olives, avocados, nuts, fish (salmon, tuna, pilchards, mackerel, herring).
Photo by Martijn van Exel