For decades now the government had been advising people to follow a diet that is based around starchy carbohydrates and to limit their fat intake, particularly of saturated fat. They make the following recommendations regarding % energy derived from different macronutrients:
- Protein: 9%
- Fat: less than 35%
- Carbs: at least 55%
However, people have criticised these recommendations in light of the rise in obesity. Others even suggest that they have caused the obesity epidemic. In response to this, the low carb diet approach has gained strong support as the best way to eat for weight loss and weight maintenance.
We look at some of the evidence around low carb and higher carb diets. We suggest that the approach is one thing, but for losing weight – quality matters.
The benefits of a low carb diet
Here are some of the cited benefits of a low carb approach to losing weight.
- Rapid weight loss. A study found that the Atkins diet was superior when it comes to weight loss. You’ll find countless blogs and reviews documenting the efficacy of the low carb approach.
- A decrease in fasting insulin and glucose.
- A reduction in blood triglycerides.
- A lowering of blood pressure.
- A reduced need for medication. A study found that a low carb diet is more effective for people who have insulin resistance.
- In this article, the author argues that a low carb approach should help you retain muscle.
- One study showed increased energy expenditure on a low carb diet.
- A low carb diet is good at suppressing appetite. There are two main reasons for this. First, they tend to be high in protein, which is very satiating. And second, insulin levels are kept low and blood sugar is very stable.
If you search, you’ll find numerous studies about the efficacy of a low carb diet for weight loss, countless advocates and several websites dedicated to low carb or keto diets. The evidence that a low carb diet is effective for weight loss is unequivocal.
But it’s not the only approach. You’ll no doubt have read about all sorts of different methods for weight loss, a lot of them with catchy names and what seems like a rational explanation.
Of course, any diet will work if you maintain a calorie deficit. It’s that simple.
As you might expect, low carb has some downsides and its detractors. Let’s take a look at some of the concerns.
The concerns about a low carb diet
Above, we only presented the positive aspects of a low carb diet. Here are some downsides:
The benefits aren’t unique
First, let’s critique the cited benefits of rapid weight loss, decrease in triglycerides, reduction of fasting insulin and glucose and decreased blood pressure. You’re going to get those on pretty much any diet, by merely maintaining a calorie deficit, and especially if you exercise. When you lose weight, you improve your fat oxidation and insulin sensitivity, decreasing triglyceride levels and fasting glucose and insulin. And blood pressure correlates with weight loss, which we see all the time with our clients.
And finally, if it’s a diet, well then you’re going to lose weight! Why might low carb be more rapid than a standard diet? Because when you lose your carb stores, you lose a lot of water used to store the carbs. If you deplete your carb stores, you could lose around 2kg in non-fat weight. Might the proponents of a low carb approach be ignoring this point?
Weight loss slows
While there is initial rapid weight loss, weight loss slows. This could be due to reduced thyroid output. Insulin, which you release in response to carbs, is important for the conversion of the hormone T3 into T4, the active thyroid hormone. A drop in thyroid output and a reduction in metabolic rate are often cited concerns about a low carb diet. Even so, you’ll still find low carb advocates who have a rational explanation for the drop in thyroid output.
Why is a reduction in metabolic rate a concern? Because your calorie deficit might be eroded by a reduced energy expenditure, making it difficult to lose more weight and more likely you’ll put the weight back on.
Loss of muscle
Many studies report a loss of lean body mass. One study lists it among the concerns for low carb, while this one measure losses in lean body mass amongst its study participants. Studies on mice, which can be highly controlled, also show that a low carb approach leads to a lower lean body mass. Still, despite many reports of lost lean body mass on low carb diets, you’ll find articles that suggest low carb protects muscle.
Another study suggest that any diet will cause muscle loss: if you lose weight, you lose muscle. We know that this is not the case. We have had several clients lose body fat and gain muscle at the same time: you need to have the right approach – more on that later. If you’re interested in finding out more about why carbs help you to preserve lean body mass, have a look at our earlier blog on maintaining muscle.
Worsened health markers
You get an increase in urinary calcium, increased LDL cholesterol and rises in blood homocysteine levels. What does this mean? Well, first, if you’re losing calcium in your urine, it must be coming from – you’ve guessed it – you bone. That’s bad news for anyone concerned about osteoporosis.
Second, LDL cholesterol is your ‘bad’ cholesterol and is associated with increases in heart attacks and strokes.
Third, elevated homocysteine, like LDL cholesterol, has been associated with increases in blood clots, heart attacks, and strokes, caused by plaques on artery walls. These concerns with low carb diets – muscle loss, calcium loss, raised LDL cholesterol and elevated homocysteine – are highly undesirable and do not justify the reported benefits of rapid weight loss, reduced insulin, blood sugar and triglycerides. At least not when you can achieve these things with other diets by merely losing weight and exercising.
High fat content
Low carb diets are generally high in fat. Well of course they are, that’s the point! But there’s a problem with that for many low carb followers.
It’s challenging to get enough calories without increasing saturated fat intake. Some keto dieters will tell you it’s OK to get saturated fat, that you need fat in your diet and that your body will burn it off. They’ll eat full-fat dairy and fatty meats as part of their overall fat intake. Yes, you need fat in your diet, but from a physiological perspective, you don’t need saturated fat – you can make the stuff! You can’t make the polyunsaturated essential fatty acids, but you can make saturated fat.
One study lists some of the effects that saturated fat has on the body. These include increased production of free radicals and inflammatory molecules; cell death; a reduction in autophagy and lipid droplet formation, leading to toxicity; the production of ceramides leading, ultimately, to cell death. And, of course, saturated fat is closely associated with increases in bad cholesterol and artery thickening.
Don’t be fooled into thinking your body will deal with the saturated fat: it won’t. I know this, having been keto myself many years ago for a whole year and being fortunate at the time to have an annual well-man check-up: my bad cholesterol shot through the roof and the physician on duty was quite shocked. Another study states that on a low carb diet, it’s crucial to control saturated fat intake.
You’ll have reduced energy for resistance training workouts. I know this from first-hand experience during my keto year. But you don’t have to look far to find academic research to confirm this. This is a double whammy for your muscle. For a start, you’ll experience muscle loss with a low carb approach. Second, just when you could do with maximising your power output during resistance training to spare your muscle, you’ll find you have reduced energy levels.
Low nutrient content
You’ll miss out on nutrients. I don’t even have to find an academic paper on this point. It’s just obvious that you won’t be eating fruits, whole grains and tubers, some vegetables and probably not lentils, beans and chickpeas either. And even with vegetables, you’ll be limited to how much you consume. That’s a massive omission of essential health-giving nutrients.
Low fibre intake
You’ll be low on fibre. With fruits, veggies, pulses and wholegrains missing, you’ll be struggling to get enough fibre to meet the recommended amount of 30g a day. That’s bad for colon health and bad for your microbiome.
It’s unproven long term
It’s not proven that a low carb approach is better than any other method. This paper, as well as giving a rundown of the pros and cons of low carb, concludes that low carb is not superior to different approaches and that the long term efficacy of the approach is yet to be determined. Another paper reviewing low carb also recognises that the approach is not proven long term.
High carb diets
Given that the government recommends a particular approach to diet, and it’s relatively similar to that in other countries, notably the US, it makes sense to compare low carb to this ‘standard’ Western diet. We’ll refer to this as a high carb diet, since ‘at least’ 55% carbs by energy are a recommendation of this diet.
What’s good about a high carb diet?
Referring to the Eatwell plate referenced earlier, there are plenty of good points. It:
- Encourages fruit and veg intake
- Is high in carbs, which has the benefits listed above, most notably the preservation of lean body mass.
- Lists low-fat dairy as a recommended food source. That will help you preserve calcium as you lose weight
- Encourages the intake of healthy fats and limits saturated fat.
What’s bad about a high carb diet?
Again, referring to the Eatwell plate:
It is a low protein diet
At 55g per day for men, the government’s advice is 9% protein. In my view, that’s too low to help with satiety and not enough to help preserve muscle. The US government recommends between 10-35% protein. You can bet your bottom dollar that the US government conducted extensive research to confirm that it is safe to go up to 35% for protein. That’s great if you want to feel fuller for longer, and great for preserving muscle.
The carbs in the picture are all high GI
And what’s worse, they suggest basing your meals around those carbs. Bread, breakfast cereals, white rice, white potato, bagels. Bagels! What were they thinking! But even the suggested swaps in this reference are not great. Wholemeal bread is still a high GI food and bran flakes, like all breakfast cereals, are high GI (All-Bran is low GI, but not bran flakes).
High GI foods are going to encourage poor eating behaviours and suppress fat burning due to high insulin levels. I think GI is an important point. Millions of obese people have successfully lost weight, only to regain it. It’s not losing it that’s difficult, it’s keeping it off.
The factors affecting weight regain include how filling a food is, the ability of the food to swell the stomach and the protein content, among other things. This study concludes that a high protein, low GI diet is best for avoiding weight regain. In this same reference, they state that the diet with low protein and high GI carbs was the worst for weight regain. That describes the Eatwell plate! No wonder we have an obesity epidemic.
It allows the consumption of processed food such as cakes and sweets
They state that they are not needed in our diet, but it’s allowed anyway. Call me draconian, but I think you should cut them out altogether. I know that they say a little bit of what you fancy does you good. And in terms of health, a bit of chocolate or cake occasionally isn’t going to make much difference. But the temptation and the cravings will always be there if you have these things in the house. Our genetics predispose us to get addictions and cravings for instantly gratifying foods because of the pleasure response they produce in the brain. My advice would be just not to go there. Keep them out of the house and get over them.
Losing weight – quality matters
So, if low carb has its flaws, and the high carb diet promoted by the government encourages people to become overweight, then what’s the answer? To me, the issue here is quality.
For losing weight – quality matters. There are some laudable notions in both low carb diets and the government’s high carb diet. But too often the low carb approach is adopted without sufficient care for health. And, while it’s good that the government espouse a higher carb intake, their suggestions as to what constitutes acceptable carbohydrate sources is going to promote overeating and undesirable insulin responses.
With a move towards quality, you can largely overcome the shortcomings of both approaches. Studies that compared a low carb and high carb diets have shown that, when the participants follow a high-quality diet, both strategies are effective. .
So, what constitutes quality? Here’s my view:
Get quality protein
To me, this means three things:
Get enough of the stuff
The government’s recommended 9% is neither going to preserve muscle nor keep you full up. We’ve written before about maintaining muscle and appropriate protein intake but, in summary, about 1g per pound of lean bodyweight is a good number to aim for. I know we are mixing metric and imperial there, but it just rolls off the tongue better than any of the other recommendations.
Avoid protein sources high in saturated fat
Don’t believe that you will burn off saturated fat – it’ll worsen your health. Shun the full-fat dairy, sausages, processed meats, salamis. And certainly don’t cook with lard or butter. A good deal of the health issues associated with low carb are caused by excessive saturated fat intake. Instead get some oily fish as a protein source or choose lean proteins and supplement with low carb healthy fats from avocados, nuts, seeds and olive oil. These fats will improve your health.
Get good quality protein
Not all protein is as good at helping you preserve lean tissue. Animal protein, including dairy, has a better amino acid protein than vegetable sources. There are some vegetable sources of whole protein, such as soya products or quinoa. Or you can food combine to make your meal a complete protein, even if the components are incomplete.
Get low GI carbs
Traditional sources of carbs as listed on the Eatwell plate are not going to give you a healthy insulin response. If you’re young and sporty, these sources are OK. But if you’re sedentary or getting on a bit like me, you’re better off choosing alternatives.
The right choices are low GI. Studies have shown that basing your diet around low GI carbs with plenty of fibre is the most effective way to lose weight.
Go heavy on fruit and veg
Most fruit is low GI. Apples are around 35 and cherries are at 22, for example. Fill your boots. Nearly all veggies are low GI too. Shovel them in; they’ll deliver a lot of healthy nutrients and help you stay full, whilst also producing a healthy insulin response.
Include lentils, beans and chickpeas more
These are excellent sources of fibre, protein, slow-digesting carbs and healthy nutrients. Base at least one meal a day around foods in this group.
Find low GI whole grains
- Milled oats are OK, at around 50 on the GI scale, but pinhead oats are better.
- Barley is low GI.
- Wholegrain basmati rice is your best bet for low GI rice.
- Some wholegrain sprouted breads are low GI.
You get the idea. There are plenty of options here but, if you’ve been choosing traditional Eatwell carbs, they won’t be in the supermarket aisles you usually go down. And you’ll have to find new recipes and meals. But it’s worth it. And once you’re in the swing of things and enjoying rude health, you won’t want to go back. One final note on this: you don’t have to base a meal around a carb source. People tend to underestimate the calorie content of their carb source and will have too large a portion. Either keep the portions moderate or don’t base your meal around them.
Choose quality fats
You don’t really need to consume saturated fat because you can make it. But you do need to consume essential fatty acids, especially omega 3 and 6. Fatty fish is an excellent source of omega 3, as is flaxseed and walnuts. And you’ll get omega 6 in nuts and seeds, sunflower oil, eggs and animal protein sources.
You’ll get small amounts of fat from your sources of wholegrains, protein and veggies. But when you need to add fat to your meals, choose sources such as nuts, seeds, avocados, olive oil, oily fish and eggs.
Do the right exercise
Exercise will improve your physiology and, particularly, your capacity to oxidise fat.
Resistance training, in particular, is crucial for maintaining lean body mass as you lose weight, especially if you are low carb. A number of the studies cited make this point. You have to work hard to preserve your muscle. We’ve had clients who lose fat and increase their muscle, but they all have one thing in common: they work their socks off in their workouts. They put everything into it. You can lose a lot of weight without losing muscle, but you need enough protein, and you need to work hard in the weights room.
Any diet where you are in calorie deficit will help you lose weight. Whichever you choose is, to some extent, a matter of preference. If you are insulin resistant or you tend to struggle with hunger and cravings, you might prefer a low carb diet. However, in general, you’ll get the best long term results with a higher carb diet. That’s mainly because of the additional fibre content and retention of muscle.
Whichever diet you choose for losing weight – quality matters. In fact, it’s crucial. Losing weight requires reducing your calorie intake, and this necessarily means reducing your opportunity to get health-giving nutrients. Don’t make it worse by choosing low-quality food. You’ll find it harder to lose weight if you make the wrong choices.
Treat yourself like an athlete. Lose weight slowly to preserve muscle, get enough protein, perform resistance training. But above all, make sure what you eat is high quality: get plenty of low GI carbs, avoid processed meats and make sure your fat intake is healthy.