There’s a general notion in nutrition that, as far as body weight is concerned, ‘a calorie is a calorie’. In other words, the impact that food has on body weight is ultimately down to the number of calories we consume, and has nothing to do with the form that they come in. However, as I explain in my just-published book, Escape the Diet Trap, there are several reasons why different forms of calories may have different ‘fattening’ effects. I also explore the science behind this as well as detail more than a handful of studies which appear to provide evidence for the notion that a calorie is not necessarily a calorie after all.
This week, I came across another study which provides evidence for the idea that different forms of calorie can have differing impact on body weight (as well as body composition) [1]. Here, in brief, is what the study entailed:
25 adult men and women spent some time being assessed to ascertain the number of calories required to maintain a stable weight. Then they were randomised to one of three diets, each of which contained a different amount of protein (low, normal and high). The number of calories contributed by protein, carbohydrate and fat respectively for the three diets was:
- Low protein – 6:42:52
- Medium protein – 14:41:44
- High protein – 26:41:33
You’ll notice that percentage of calories from carbohydrate was essentially the same for all three diets – only protein and fat intakes were different. The individuals were fed these diets in a very controlled environment for a period of 8 weeks.
One other thing: these diets supplied about 40 per cent more calories than estimated to be required for weight maintenance. This equated to overfeeding of an average of about 950 calories a day.
The researchers assessed a number of body parameters including body weight, fat mass and lean mass (muscle, essentially). Here’s a summary of the findings (all figures are kilograms):
| weight change | lean mass change | fat mass change | |
| low protein | +3.61 | -0.70 | +3.66 |
| medium protein | +6.05 | +2.87 | +3.45 |
| high protein | +6.51 | +3.18 | +3.44 |
In summary, the most notable findings were, I think:
- The amount of fat gained was essentially the same (irrespective of dietary composition).
- The normal and high protein diets both led to an increase in lean mass (muscle) that was roughly equal in weight to the fat that was accumulated.
- The low protein diet led to less weight gain overall, principally because it did not contribute to lean mass gain (actually some lean mass was lost).
The main conclusion drawn by the authors was that when people are overfed, the fat they accumulate is not influenced by the amount of protein they consume (only the total number of calories).
That observation is supported by their data, but another way of interpreting the same data would be to say that when people over-consume food, the percentage of calories coming from fat have no bearing on fatness. This perhaps contrasts with what most people might imagine, as many believe is easier for dietary fat to end up as fat in our tissues than carbohydrate or protein.
Another thing that this study appears to show is that when protein is low and fat is high, less weight is gained overall than when, relatively speaking, protein is higher and fat is lower. This finding does appear to provide evidence that contradicts the idea that all calories influence body weight identically whatever their form (a calorie is a calorie).
What is also true is this study also found that if we’re looking to maintain (or perhaps build) muscle, it makes sense to eat adequate amounts of protein. The diets richer in protein led to improved body composition compared to the low-protein diet.
OK, one could argue there’s some interesting stuff here, but I would also argue that this study tells us very little indeed that has real relevance to people seeking to lose weight or maintain a healthy weight. And that’s because in this study, the individuals were essentially compelled to eat much more than they ordinary would. In the real world, when people overeat they usually do it all by themselves (without being asked to or remunerated for it).
So, what is it that causes people to overeat? There are many factors here, but let me list just a few:
1. Too little protein
Study after study shows that for a given number of calories, protein sates the appetite more effectively than either carbohydrate or fat.
2. Too little fat
Quite a lot of people find that for food to be satisfying, it helps for it to contain a decent quantity of fat. I have this going on: a chicken leg leaves me feeling much better sated than a dry breast.
3. Too much carbohydrate
Eating a carbohydrate rich diet can cause cycles of blood sugar high and lows. Lows in blood sugar (or even just rapidly reducing sugar levels) can cause hunger and food cravings (particularly for sugary/sweet/starchy foods).
4. Too much carbohydrate again
A lot of carbohydrate can cause elevated levels of insulin – the hormone chiefly responsible for fat storage in the body. This can make fat hard to shift from the fat cells. That’s a shame, because fat liberated in this way can provide fuel for the body, and is essentially food. It is possible that liberated fat helps quell the appetite through this mechanism, but that’s not going to happen so well if the diet is rammed full of carbohydrate and causing chronically elevated levels of insulin.
Let’s put this in reverse, though. Imagine what would happen if less carbohydrate was eaten. Insulin levels may well come down and now fat can get out of the fat cells, where upon it can ‘feed’ us and keep us nicely satisfied. The proportionally more fat and protein in the diet might help here too. Time and again I’ve seen individuals who adopt a lower-carb diet relatively rich in protein and fat they automatically eat less (often several hundred calories less each day) than they ordinarily do, and the research bears this out too.
Overfeeding studies like the one described above can be interesting, but they don’t really help people who want to lose weight. What we really need to know if what to eat to facilitate fat loss and keep hunger at bay.
References:
1. Bray GA, et al. Effect of Dietary Protein Content on Weight Gain, Energy Expenditure, and Body Composition During Overeating – A Randomized Controlled Trial. JAMA 2012;307(1):47-55
7x8x950/7700=7.36 kg. If the often quoted 3500 K/ pound number was true, we should see something like 7.4 kg change. Oh well, I know this is because nobody look at biological efficiency, personal variation in Atwater factors, and similar. It takes energy to make fat, and energy to degrade it. Also, there is a 2 to 4 kg change with glycogen, with a caloric density of slightly over 1.0.
What this study hints at is we need adequate protein, and fat is less efficient at putting on fat than carbohydrates. I agree, weight loss and weight maintenance is all about satiation, and satiety, typically resolved by higher fat ingestion. This assumes that are not other social-emotional-psychological-chemical reasons for indulgence, which there usually are.
Can I get a copy of your book?
I would appreciate it if sometime, Dr Briffa, you would explain how researchers measure ‘lean mass change” and “fat mass change”. Thanks.
Only after joining your community did I learn why I was producing too much insulin, with the accompanying blood sugar swings problem. I bought a copy of ‘Escape the Diet Trap’ yesterday and I’m going to move to adopting your eating recommendations. The only trouble is that I’m brainwashed into the high carb/low fat route and it feels very strange to reverse that eating habit in my mid-60s!
I found your article in The Times Weekend (7 Jan) most interesting. I had a creful look thru the What to Eat section. I worked out what would happen if I took out of my diet rice, pasta, bread and breakfast cereals. Result: I would eat almost nothing! Weight loss would be huge but death would come much sooner than I would want!
I actually think it is an interesting study. It shows that undereating protein is not a good thing for your LBM, that’s a message vegans should hear.
I also find it interesting that there are two things that also seem to correlate: % of fat gained and % of carbs in each diet. It might be coincidence, but perhaps not.
Don’t blame insulin. Protein causes a higher insulin response than carbohydrate, leading us to understand that it’s not insulin that matters in fat storage. Check it out: http://musclegeek.wordpress.com/2011/11/15/insulin-not-the-enemy-refined-grains-are/
I’ll second the previous comment about not blaming insulin, especially as protein seems to promote weight loss DESPITE it increasing insulin just as effectively as carbs. It seems that the real reason carbs promote weight gain where protein doesn’t is in promoting satiety and fullness. It’s difficult to eat excess protein rich foods, and very very very easy to overeat carb rich foods…
Cheers,
George Super BootCamps
Dan and George
Although, unlike carbohydrate, protein stimulates the release of glucagon, which mitigates the fat-storage effects of insulin.
Dr Briffa,
What about high protein diets raising the IGF-1 ( Growth Hormone) which although causes muscle growth and bone, it also lead to ageing and growth of disease tumours? especially animal protein
After years of counting calories in and calories out, creating deficits every day, my weight has not been moving at all. Speaking to my doctor, all I heard was “eat less, move more.” Nothing seemed to help. Now I feel like I am finally reading research to support what I have been feeling in that it is more than just calories in versus calories out. I am eager to put some of this new found information about what the calories in should be and see what happens. thanks for posting this.
Hi John,
I bought your latest book and have been through it twice now. I lost 5 stone over the last 12 months and now I am for vanity reasons working on a low body fat plan. My diet, of my own design and, without scientific support is a low sugar diet and slow carb diet – mostly because I had learnt from experience that high GL foods caused me big problems with appetite.
So, I know that much of what you point to checks out with my personal trial (assuming I haven’t factored out some other influence) – low GL and fewer carbs in general has been helping me to eat sensibly.
I stuck to a low fat diet because I had believed the universal truth that high fat is bad for you. 20g per day was my limit. About half way through the diet I learnt that some fats are healthy and should be included but I found the foods so that contain those fats to be very calorific (Oily fish & oils in general) so I mostly avoided them to stay inside my calorie target.
I am taking on board your advice about fat being no worse than any other calorie, and in fact better than carb calories, because of the no insulin response needed to metabolise fat. However, I still count my calories (I was trying to learn what calorie limit is sensible for my own personal weight maintenance as a negative feedback loop).
I noticed that you often refer to the studies where a higher fat/higher protein/low carb approach worked to aid weight loss where the subjects were free eating but ultimately you quote their average calorie intake. Often the number for loss/maintenance was in the region of 1600 calories per day.
Do you think there is a roll for calorie counting even in a low carb diet? I fear that years of over eating might mean that I am unable to hear my body’s appetite signals clearly enough. E.g. I have been known to eat a kilo of steak with veg and fries. Twice in the same week. I admit that I was not hungry after the meal but I was no less hungry for the following meal (eating by the clock perhaps). In fact, as I write this question, I realise that perhaps I have never been in a situation where “I couldn’t eat another thing” – although I know that high GI carb foods can turn this state from an “Eat if its available” to craving.
So, in summary, is there a place for calorie counting within the low carb diet and if so do you believe the standard measure (BMR calculators) are suitable for the job?
Hello Dr Briffa – In your book Escape the Diet Trap you talk about the fact fat does not raise insulin (page 67). A study in AJCN published after your book would have gone to press, talks about the effect of fat on the incretin effect and appears to contradict this?
Carel et al – Contributions of fat and protein to the incretin effect of a mixed meal
Am J Clin Nutr 2011 94: 997-1003.
I would be interested in your thoughts on this study. Thanks.
Is it not safe to assume, if you eat less carbs you also automatically get less calories? Because many high carb foods is high in calories. So less carbs=less calories=weight loss. Or am I simplifying the issue?
I read the Times article, bought and read the book and have embarked on the diet largely because most of the more sensible diets I have tried have not resulted in weight loss of any note, not even when I added in regular exercise. Like Lynn’s comment above, I, too, believe that there is more to weight loss for some people than the simple equation endlessly quoted of fewer calories in and more exercise being the only answer.
I have followed the guidelines in the book, I don’t buy bread anymore, I haven’t had pasta, potatoes or rice in the last 5 weeks, apart from on a couple of occasions when I ate only a small portion. I have pretty much avoided cakes, biscuits and sweets. I haven’t exercised more but I do walk the dog twice a day for about half an hour. Weight loss? Negligible. I eat eggs from our own hens, try to only eat grass fed beef, drink raw milk, source bacon and sausages from outdoor reared pork and try to eat plenty of vegetables and fruit, organic where possible. I have also started taking D3, already supplement with B1, magnesium citrate and Krill oil. I don’t really experience hunger so binge eating and snacking has never been a problem. Why isn’t it working?