Insulin, carbs and weight loss - what’s the connection?
There’s a lot of confusing information out there about how carbs and insulin make you gain weight followed by theories about how following a low carb diet can help you quickly lose weight and control your insulin levels.
What is this theory and what are the claims?
The carbohydrate-Insulin model
Dr David S Ludwig, the man behind the carbohydrate-insulin model of obesity argues that high carb foods change your hormones, cause you to become more hungry and slow down your metabolism, therefore making you gain more fat.
Since this argument has now gained traction, especially among many masters athletes hoping to shed some more fat, I think it’s important to look at the science around it so that athletes can make a well informed decision as to what kinds of diet to follow and what the benefits or implications may be.
To begin, let’s start with the most obvious question…
What is insulin?
If you’ve hung around the fitness industry long enough, you would have heard of the word insulin being thrown around conversations to do with weight gain and weight loss.
So what is it exactly?
Insulin is released by the pancreas to help your body regulate blood sugar. So when you consume a meal high in carbohydrates, your body will release insulin as a response to bring down your blood sugar to it’s normal levels.
Different people will experience insulin release differently.
Individuals with a lower body fat and/or more active than the average population (athletes for example) may be insulin sensitive, meaning that they only need a little bit of insulin to regulate their blood glucose.
Insulin resistance on the other hand is a condition where your body no longer responds to insulin as a result of your pancreas not being able to keep up with the demands of the cells’ increasing resistance. This can lead to pre diabetes if left untreated.
Does insulin make you store more fat?
Some folks may argue that an increase in insulin stops the process of “fat burning”. This statement isn’t entirely inaccurate, but to understand why that doesn’t necessarily equate to more “fat gain” you’d have to understand that science a little more.
In comes lipolysis…
Lipolysis is the breaking down of fatty acids into the bloodstream so that we can use fat as energy.
Insulin actually thwarts this, and because of this, many have misunderstood this to mean that insulin impedes fat loss.
That is not the case.
To make matters even more confusing, insulin actually stimulates lipogenesis, meaning that it encourages fatty acids to move from your bloodstream into your fat cells, in other words it allows your body to move into a fat storing mode so that you can use it for energy at a later time.
So on the surface it does sound like that theory has legs…
But before you run to your kitchen cupboards and begin throwing out sacks of rice and popcorn, hear me out.
The process of insulin turning carbs into stored fats only happens in response to the body intaking more carbs than it needs. In other words, if you taking in more calories than you are expending, the carbs you consume will indeed get stored as fats.
So does insulin encourage fat storage and stop “fat burning”?
Kind of, in a sense, however, not in the way that many people think because it is not as simple as it sounds.
Let me explain.
Insulin’s jobs is to maintain blood sugar levels so when you increase food intake, it will get to work on the foods that have just been released into the body rather than ask the body to release energy that is already in storage.
Simply put, if insulin is high your body will slow down on “fat burning” but only because there is currently other sources of fuel in your body, specifically carbohydrates.
This does not mean that your body will completely stop burning fat because of insulin. It’s a process that happens on a sliding scale depending on what is in your body at that particular time.
Does Insulin make you hungrier?
Back when I was a low-carber, I believed this too…
One of the arguments for a low carb diet was that a spike in insulin would leave you hungrier as a result of fatty acids getting shuttled out of the bloodstream triggering a “starvation” response from the body, hence causing it to feel more hungry.
What’s interesting however, is that there is evidence that insulin actually plays a role in appetite regulation, helping you to feel satiated more quickly. There are however, a long list of hormones that are also involved in appetite regulation.
It’s probably safe to say that avoiding all carbs as a means to avoid a spike in insulin will not solve the obesity epidemic.
How does the metabolism fit in all of this?
It’s hard to avoid the word “metabolism” when discussing fat gain and fat loss so here’s where it all fits in.
If you are a frequent visitor of my blog you would by now understand that a drop in body weight for a prolonged period can decrease your metabolism, hence why I do not encourage long fat loss phases.
The theory that insulin and carbs cause weight gain proposes that because insulin makes fatty acids move away from higher metabolic parts of the body like muscles tissue into fat cells, it would therefore slow down metabolism.
Makes sense right? Well, it was sorta disproved.
A few studies have tested this theory and found that as long as the protein intake and overall calories were matched, regardless of whether you were on a high carb diet or low carb diet, the results were similar. In fact, what’s interesting is that the authors found that the group that followed a high carb diet actually expended 23 more calories per day.
Well, there goes that theory….
So why is the low carb diet still so popular?
In comes the old argument…
“I gave up carbs and I lost loads of weight”
Yes, this isn’t uncommon and we will explore some of the reason why that could be happening:
Less ultra processed foods being consumed, and since ultra processed foods like and donuts and cakes tend to be calorie dense, this means that minimising those foods lead to an overall calorie deduction
Increased protein intake which can lead to greater levels of satiety, resulting in overall less calorie intake
Water retention: for every 1g of carb consumed, around 4g of water is retained, this means that suddenly going from a high carb diet to a low carb diet could lead to sudden weight loss. However, this weight loss is water weight not fat mass.
Conclusion
The laws of thermodynamics will always apply when it comes to weight loss and weight gain. Calories in vs calories out will always determine whether an individual loses weight or not. This is not to say that eat less, move more will always work.
You can eat very little and still struggle to lose weight, this isn’t your fault, but it is still thermodynamics at play. It isn’t fair, but energy balance is multidimensional.
The human body is a complex set of structures, and since weight loss combines many variables (many of them outside of your control), it can be frustrating trying to find a strategy that is right for you.
This means considering your biometrics, volume of training, the kind of sport you do - endurance athletes may require an even higher volume of carbs than lifters for example - food preferences and life circumstances.
Remember that weight loss is multifaceted and in order to achieve sustainable results you have to consider all the elements that are involved in your overall health and what each strategy might mean for your performance as an athlete.
Did you find this blog helpful? Comment below.
References
Flegal KM, Kruszon-Moran D, Carroll MD, Fryar CD, Ogden CL. Trends in obesity among adults in the United States, 2005 to 2014. JAMA. 2016;315(21):2284-2291.
Mansoor, N., Vinknes, K., Veierød, M., & Retterstøl, K. (2016). Effects of low-carbohydrate diets v. low-fat diets on body weight and cardiovascular risk factors: A meta-analysis of randomised controlled trials. British Journal of Nutrition, 115(3), 466-479. doi:10.1017/S0007114515004699
Hall KD, Guo J, Speakman JR. Do low-carbohydrate diets increase energy expenditure? Int J Obes (Lond). 2019 Dec;43(12):2350-2354. doi: 10.1038/s41366-019-0456-3. Epub 2019 Sep 23. PMID: 31548574; PMCID: PMC8076039.
Bradley U, Spence M, Courtney CH, McKinley MC, Ennis CN, McCance DR, McEneny J, Bell PM, Young IS, Hunter SJ. Low-fat versus low-carbohydrate weight reduction diets: effects on weight loss, insulin resistance, and cardiovascular risk: a randomized control trial. Diabetes. 2009 Dec;58(12):2741-8. doi: 10.2337/db09-0098. Epub 2009 Aug 31. PMID: 19720791; PMCID: PMC2780863.
