What's the 'optimal diet' for fat loss?
Let's face it, when it comes to the 'fat loss' industry, it's a bit of a minefield out there in terms of the different diets we could be following... keto, vegan, carnivore, 5:2, IIFYM, low carb, time restricted eating, pescatarian, mediterranean, paleo, intermittent fasting etc etc.
Many of these diets are promoted as the top choice for fat loss, so what's really going to get you results?
Let's take a look at the PROS AND CONS of some of these more recent trends:
Following an IIFYM (If it fits your macros) style diet where the quality of the food is not taken into consideration may work in the short term but if your diet is still high in refined foods this will be causing systemic inflammation, poor blood sugar regulation and disrupted gut health, all of which will hinder fat loss. Your ability to handle these refined foods may partly be dictated by your genetics, activity levels, detox pathways, gut health etc.
With diets based around extreme and prolonged calorie deficits you may see some short term weight loss but this will be detrimental to your metabolism long term, down regulating the thyroid and resulting in rebound weight gain. There are ways to experiment with calorie deficits such as the 5:2 diet or some time restricted eating/intermittent fasting, all of which will boost insulin sensitivity (which is one of the factors that may promote fat loss). However these may not work for everyone, particularly those with high stress levels, impaired thyroid function and also just by the nature of being a woman (biologically) means you would need to tread more carefully with fasting (our hormones are more sensitive to calorie deficits/fasting)
Some people will do really well on a keto diet (this is largely due to the reduction in refined carbohydrates and again improved insulin sensitivity), however this may not work for others who are inadvertently feeding a bacterial overgrowth. Poor gut health, particularly dysbiosis (imbalance of good and bad bacteria in the intestines) is significant to fat loss because low levels of beneficial bacteria such as akkermanisa and christensenella are associated with poor appetite regulation and increased body fat storage. These beneficial bacteria require adequate intake of polyphenols and resistant starch, both of which are typically low in a keto diet. It is also important to note that a diet higher in saturated fats may also fuel overgrowths of gram negative bacteria. These bacteria produce toxins (lipopolysaccarides -or 'LPS') which can cross the gut lining into the blood stream where they can go on to produce systemic inflammation associated with obesity, diabetes and heart disease. Furthermore, high levels of bacteria such as klebsiella have been found to up-regulate glucose transporters in the gut, meaning that you will essentially absorb more of the glucose (sugar) from a given meal, not only impacting your ability to maintain a healthy weight but also your blood sugar regulation. Don't get me wrong, I'm not saying a keto diet doesn't have it's place in fat loss but supporting optimal gut health alongside this diet is key.
A ketogenic or low carb diet may also be detrimental for those with low thyroid function, further reducing your metabolism. This is due to insulin increasing the conversion of inactive T4 hormone to active T3. In short, keto or low carb diets may lower your metabolism
Now let's look at the vegan diet, like anything it's possible to 'do it well' (this involves supplementation and mindful intake of adequate healthy fats and proteins) or to do it terribly (ie an excess of highly refined 'meat alternatives'). You can certainly fall into the trap of following a carb heavy vegan diet, particularly as many plant based protein sources such as lentils, beans and rice as also dense in carbs. Make no mistake, carbs aren’t the ‘bad guys’, but we want to make sure they’re not taking the place of essential amino acids and fatty acids (proteins and fats we can’t make in the body). Another element to consider is the potential to upset your hormonal balance (which has implications for fat loss) through an excess of phytoestrogens (plant compounds which can mimic/block oestrogen receptors in the body) and goitrogens (compounds which inhibit idoine uptake to the thyroid reducing metabolism). That's not to say that a vegan diet can't be part of a fat loss plan, just a fair amount of thought and planning needs to go into it.
With the carnivore diet (solely eating animal products), we may see some fat loss in the short term, but the long term implications may not be great. We run into many of the same gut health issues we do with the keto diet, except more extreme with absolutely no plant fibres to boost beneficial bacteria such as akkermansia. Much like the keto diet, a carnivore diet will fuel an overgrowth of bacteria such as bilophila wadsworthia, hafnia alvei and veillonella (some crackin' names right!) which feed off saturated fats (these guys are often found to be high in the standard western diet). Again these gram negative bacteria produce LPS (toxins) cross the gut membrane (particularly in the presence of a leaky gut) where, as we discussed with the keto diet, they will create all sorts of problems systemically including low grade inflammation and insulin resistance (all associated with weight gain).
Let's move onto the pescatarian and mediteranean diets, both typically involve a fair amount of fish/seafood much of which is extremely nutrient dense in terms of essential fatty acids, vitamins, minerals and protein. This high intake of healthy fats and protein is particularly satiating, helping to reduce cravings and promote healthy weight management. However, the downside to eating from the ocean is the potentially high toxic load, particularly of chemicals such as mercury, PCBs (polychlorinated biphenols), chlorinated pesticides etc. These high levels of toxins can place burden on the liver meaning that our whole detox system is on the back foot, including detoxing hormones such as oestrogen which may lead to oestrogen dominance and weight gain. Further more an accumulation of chemicals like mercury can cause inflammation of the thyroid including hashimotos disease (autoimmune driven low thyroid function) which will mean a decreased metabolism and increased risk of weight gain/retention.
Finally let's take a look at the paleo diet which involves eating foods that were, in theory, consumed in the paleolithic era. The basis of this diet is pretty sensible in terms of leaning towards eating whole foods, and limiting intake of highly refined and hyper palatable hydrogenated vegetable oils and refined sugar. This emphasis on food quality and avoiding foods, which will have a positive impact on your blood sugar regulation, is obviously beneficial for weight loss, however it may be too restrictive especially for those trying to reduce meat/fish consumption. That said, the basic principles and emphasis on consuming satiating whole foods is a pretty good starting point.
So after taking a closer look at each of these diets, a better way to phrase the question is ultimately what is the optimal diet for YOU to promote fat loss.....
You see the thing is there really is no one size fits all, when I recommend individual fat loss programmes they are not designed as a list of rigid rules with a strict meal plan/calorie intake/macro split. They’re designed as a guidelines to give you a whole host of tools and tweaks you can utilise to kick start your metabolism and start working towards better eating patterns, food choices, hormonal balance, digestive health and lifestyle habits, which in turn will promote fat loss.
As always, if you have any questions, don't hesitate to give me a shout.
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The content in this article is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of a qualified health provider with any questions you may have regarding your health.