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Hi, I am recently trying to lose weight via a low carb diet. But I heard that a low carb diet will:
- Deprive energy to our brain as the brain can only accept sugar as energy, and not protein and
- Cause excessive ketones to be formed, and in the long run cause liver/kidney problems.
Is it true? How can I lose weight through a low carb diet healthily? Thank you.
Thanks for the question. Dr Ethan has provided a great answer to your question and certainly diet plays a significant role in weight management or reduction.
Essentially, it’s a matter of balance. If you put more calories in than you expend, you will be in a positive balance and hence this is stored by the body for a rainy day.
In the past, when your ancestors had a less predictable supply of food, it meant that over the good times, they stored fat and in harder times, our body used these fat stores. Interestingly, ketones are a byproduct of fat breakdown and also a metabolite for the brain.
In terms of the low carb diet, much of the “carbs” that we consume are actually hidden. Even things that have been labelled as “low fat” tend to be pumped full of sugar.
To be quite honest, if you are going to try a no/low carb diet, you need to really be mindful of what you eat.
I spoke to a dietician colleague who has a special interest in sports and her advice was:
1. Low carbohydrate diets, like most diets, can cause weight loss by creating a calorie deficit. One benefit of starting on a low carb diet is that you will become more aware of the nutrient content of the foods you’re eating. If your goal is to be below XXX grams of carbs a day, then you will need to start tracking your macros, and this may help reduce intake of simple/added sugars found in soft drinks, cakes, desserts, candy, pastries, which can also be high in fat, hence higher in calories.
2. In addition, the exercise you’re doing (whether competitive sports, or leisure, or just starting out on a regular exercise regime for weight loss) may affect your macronutrient requirements. Endurance sports generally require a higher carbohydrate intake, whereas resistance training for building muscles will require a high protein intake (take note though, most of us get more than enough protein in our daily diets so there’s no need to stock up on protein shakes).
3. To go into ketosis you’ll need to do <20g/day for about 3 days. Speaking to your sports dietitian will help you structure your nutrition plan for re-fueling wisely.”
So as you can see, low carb is an option but it’s only part of the solution. Getting up and exercising plays an important role in addition to one’s diet. Mostly it’s the hidden sugars that we need to be mindful of.
Finally, as Dr Ethan says, the likelihood of triggering acute liver/renal failure from a low carb diet is unlikely provided you don’t have any pre-existing medical conditions.
Good luck with your exercise and weight loss ambitions. Please let us know how you get on!
Dr Dinesh Sirisena
KTPH Sport Medicine Consultant
Hi A – I’m gonna do a very annoying doctor thing and say that every diet has it’s own disadvantages and benefits.
However all things considered, I have chosen a low carb/relatively higher fat diet for myself after weighing the pros and cons, and also just for the fact that it suits my lifestyle and I genuinely like proteins more than carbs. I mean who wouldn’t choose a good steak over rice any day?
Disclaimer that what you’ve asked is probably in the territory of a nutritionist/dietician rather than a doctor, but I shall attempt to address your questions based on what I remember from med school and my sport medicine course a long time ago:
1. Deprive energy to brain as can only accept sugar as energy not protein
Yes, the brain cannot use proteins as energy. It uses glucose.
But fat, protein and carbs can ALL be broken down into glucose. It’s just much easier for your body to turn carbs > glucose.
You also have other forms of energy stored away in your liver and muscles, in the form of glycogen, which can again be turned to glucose easily, so I wouldn’t worry too much about depriving your brain of glucose.
Anyway – a simple solution is to not restrict yourself to protein – I eat animal fat, and good sources of fat – olive oil, salmon etc. I also eat small amount of carbs.
2. Cause excessive ketones to be formed and in a long run cause liver/kidney problems.
This will not happen if you are a HEALTHY person with no preexisting kidney problems.
There was a review study that looked at all of the published research on high-protein diets and kidney disease. The authors concluded that while high-protein diets can be harmful for those with kidney disease, they do not harm the kidneys in healthy individuals. Other studies and links here: (7, 8, 9)
3. What is the most effective method to lose weight healthily?
Diet plays 80% of the role in losing weight, exercise plays 20%.
Simple maths equation – what you burn must be more than the calories you eat. My endocrine professor at school used to say to his patients that if you are not constantly hungry – it means you are not losing weight.
Your body has an uncanny mechanism called homeostasis which basically tries to keep everything the same – your weight, body temperature etc etc. ie if you started losing weight, your body goes SHIT WE NEED TO EAT MORE, hence you get hunger pangs, and end up eating more the next day unknowingly. Which is what makes it so challenging for many overweight patients to lose weight.
If I were you, I would stick to a clear diet plan, and regular exercise regime. I like a low carb diet for losing weight.
You could also consider seeing a sport medicine doctor who has expertise in helping people lose weight safely.