What is the best ‘Diet’?


Which Diet is Best?

Zone, Keto, Atkins, Paleo, Low Carb, Carb Cycling….and so on. Few things are as transiently fashionable as a new diet plant.

Weight loss and muscle gain are both simple. Everything else is just branding.   

Currently, high-protein, low-carbohydrate diets and intermittent fasting are promoted for successful weight loss but owing to some adverse effects – especially of extremely restrictive diets - many strategies are recommended as a starter, not a long term dietary plan.

In the long term, current evidence indicates that different diets actually promote similar weight loss and the most fundamental predictor of success is adherence:  How likely are you to stick to it?

The fundamental basis of any weight-loss program is achieving a net calorific deficit from reduced calorific intake and elevated calorific expenditure (see Myth #2 - Body weight is just calories in and calories out) but the manipulation of macronutrient content in isocaloric diets (where the calorie content is the same) has been studied to determine which composition best promotes weight loss while including other metabolic benefits.

Changes in the macronutrient composition (carbohydrates, fats or protein) affect hormones, metabolic pathways, gene expression, and the composition and function of the gut microbiome that might effect fat storage (1).  So meddling with any of that can have some adverse effects.

After: Freire R. (2020) “Scientific evidence of diets for weight loss: Different macronutrient composition, intermittent fasting, and popular diets”. Nutrition. 69:110549


Low-Carb Diets

Metabolically, carbohydrates elevate insulin levels, directing fat toward storage in adipose tissue, described as the carbohydrate-insulin model (see Myth #3: Carbs are carbs) (1).  In this context, Low Carb (LC) diets claim to treat obesity because they promote reduced insulin secretion and increased glucagon, which cause a metabolic shift to higher fat oxidation (2).

LC diets can be designed to be either high fat, high protein (HFHP) such as the Atkins, or Zone diets or normal fat, high protein (NFHP) such as the Keto or Ormish diets.

However, despite the theory of the carbohydrate-insulin model, clinical trials comparing LC diets with low-fat (LF) diets where protein intake is the same, weight loss is reported as being similar (3-7) and even greater body fat loss when reducing fat intake rather than carbohydrates. (8)

An important meta-analysis of 32 controlled studies concluded that energy expenditure and fat loss were more significant with Low Fat (LF) diets when compared with isocaloric LC diets (9).

 

The ketogenic diet (KD), prescribes a minimum of 70% of energy from fat and a severe restriction of carbohydrates to mimic a fasting state and induce ketosis (10) to promote weight loss and has the additional advantages of reducing hunger and appetite (4,11). Overall, clinical trials have reported significant weight reduction (12-14), although many studies were uncontrolled (15,16).  Adverse effects such as constipation, halitosis, headaches, muscle cramps, and weakness were commonly observed (17).

Observational data have demonstrated an increase in mortality associated with the long-term LC and High Carb (HC) diets but minimal risk at 50% to 55% energy derived from carbohydrates.  They also reported that animal-derived protein and fat were associated with higher mortality, whereas plant-derived protein and fat were associated with lower mortality (18).

 

High Protein Diets

HP diets in which at least 20% of energy is derived from protein, appear to offer advantages regarding weight loss and body composition in the short term (9,19).  Popular HPHF diets, such as Atkins or Zone, promoted significant weight loss for short periods (20-23).  HP intake acts on relevant metabolic targets, increasing satiety and energy expenditure (24).  Conversely, in clinical trials >1 to 2y, evidence indicated no significant differences in weight loss (6, 20, 22, 23, 25).

HPHF diets are often associated with a high intake of animal products and saturated fat, causing detrimental effects of increased low-density lipoprotein cholesterol (26, 27).

In conclusion, in the short term, HPLC diets are suggested to present benefits for weight-loss but due to their major effects on metabolism and gut health, they should be considered as a jump-start weight loss tool rather than a diet for life.  In the long term, current evidence indicates that a different ratio of macronutrients associated with a caloric restriction in healthy diets promotes similar weight loss (9, 28).

 

Vegetarian Diets

A vegetarian plan can range from the simple exclusion of meat products to the raw vegan plan, which only includes raw vegetables, fruits, nuts, seeds, legumes, and sprouted grains (29).  Exclusion of animal products can reduce the intake of certain nutrients, which might lead to nutritional deficiencies of protein, iron, zinc, calcium, and vitamins D and B12 (29, 30).

Adoption of plant-based diets is growing because evidence has shown some health benefits when compared with omnivorous diets.  They can protect against chronic diseases, such as cardiovascular diseases (31, 32), hypertension (33) and type 2 diabetes (34), and some cancers (35).

 

Paleo Diets

The Paleolithic Diet, also called Paleo, is based on everyday foods that mimic the food groups of our preagricultural, hunter-gatherer ancestors.  This is based on the theory that the hunter-gatherer diet and lifestyle sustained humanity for 2.4 million years, causing humans to be genetically adapted to it.  profound changes in diet and other lifestyle conditions after the introduction of agriculture and animal husbandry 10 000 years ago have been too recent on an evolutionary time scale for an adjustment of the human genome (36, 37).

The Paleo diet features characteristics such as a lower ratio of omega 6 to omega 3 fatty acids and lower sodium, along with a high content of unsaturated fatty acids, antioxidants, fibre, vitamins, and phytochemicals that operate synergistically to promote health benefits (37). The diet is high in protein (20-35% of energy) and moderate in fat and carbohydrates (22=-40% of energy, specifically restricting a high glycaemic index) (38).  Finally, the Paleo diet yields a healthier net alkaline load compared with the net acid load estimated for the typical Western diet (37).

Evidence has demonstrated several improvements such as ameliorations in metabolic syndrome (MetS) (39), increase in insulin sensitivity (40), reduction of cardiovascular risk factors (41, 42), increased satiety (43-45), and beneficial modulation of intestinal microbiota (46).

Specifically, regarding Paleo diet for weight loss, scientific evidence points toward consistent reduction of body weight and body fat mass either in short- (42, 44, 49-49) or long-term studies (50-52) (42, 47, 49, 50, 52-54). Low adherence (44), poor palatability, and high costs are common issues reported by those who follow the Paleo diet (55).

As an important limitation, the Paleo diet presents a potential deficiency risk that includes vitamin D, calcium (47), and iodine (56).

 

Gluten Free diets

Gluten is a protein complex found in cereals such as wheat, rye, barley, and oats (57).  Studies have shown that the main fraction of gluten, namely gliadin, cannot be completely digested by the gastrointestinal (GI) tract, triggering an intestinal inflammatory response in susceptible individuals (58).

Evidence supports a possible obesogenic effect of gluten.  First, a cereal-based diet impaired insulin sensitivity and blood pressure control and increased the levels of C-reactive protein in pigs (40).

In rodents, two pioneer studies reported obesogenic effects of gluten using the nutritional model of obesity:  A HF diet added with gluten induced higher weight gain, adiposity, blood glucose, inflammation, and IR, partly by reducing the thermogenic capacity of adipose tissues (59, 60).


Mediterranean Diets

The Mediterranean diet is a balanced diet characterized by high consumption of vegetables, fruits, legumes, whole-grain cereals, seafood, olive oil, and nuts. Red meat, dairy and alcohol are recommended in moderation (61).  The Mediterranean diet is rich in plant-based foods, having high levels of antioxidants and dietary fibre, and low glycaemic load compared with other diets (23).  It also has an adequate ratio of monounsaturated to saturated fatty acids.

Studies reported weight loss associated with the Mediterranean diet in the short (62-64) and long term (23, 64).

However, meta-analysis studies observed that the overall amount of weight loss was similar compared with other diets in overweight and obese individuals (65, 66).

Due to the high nutritional quality of its food composition, the Mediterranean diet has been considered a healthy eating pattern for many conditions.

The Mediterranean diet has been associated with a reduction of inflammatory markers (67), and important reduction of cardiovascular risk factors and mortality (67, 68).  Moreover, this diet was efficient in decreasing inflammation (62) and cardiovascular risk even in the absence of meaningful weight loss (69). 

 

Summary

  • Neither Low Carb nor High Carb diets are as effective as Low Fat Diets in weight loss.    Carbs are important as long as they are the right carbs.

  • High-Protein diets are effective at kick-starting weight loss but the high protein intake and the associated intake of saturated fats, both have long term health risks.

  • High vegetable intake is widely supported for both weight loss as well as other health benefits but and exclusively vegetarian diet restricts the intake of other essential nutrients including protein, iron, zinc, calcium, and vitamins D and B12.

  • Both a Paleo and Mediterranean diets have great health benefits with few disadvantages.   The Mediterranean diet is more palatable, advocating the odd glass of wine and plenty of bread and cereals which the Paleo diet excludes.

  • Gluten is really of no benefit, bringing nothing to the party other than weight gain, gastrointestinal irritation and elevated blood glucose.

So a balanced approach might look something like:

The Slow Carb Diet.


❌ Avoid fruit.  Another easy way to reduce unnecessary calories (see Myth #1: Calories are Calories and Myth #4: Fruit is good for you) but capitalise on vegetables and pluses for nutrient needs and essential fibre.

❌ Avoid white carbs. (see Myth #3: Carbs are carbs) but embrace good quality, non-stary carbs (50-60%), a reasonable amount of unsaturated fats and a moderate (20-30%) amount of protein.

❌ Don’t drink calories. This is an easy way to reduce unnecessary calories (see Myth #2: Calories In vs. Calories Out), as fluid calories, in the form of a creamy latte, a pint of beer or glass of wine, are primarily for taste and reward but provide no other benefit. They are entirely unnecessary calories. Just drink plenty of water, black tea or black coffee. Or even a zero sugar energy drink. Aspartame is not great for you, but you need to drink a TON of it before it can trigger known health risks (Myth #6: Water = Good, Caffeine = Bad.)

✅ If you want to lose fat, aim for a calorie deficit by avoiding white carbs and fat. If you want to lose fat but gain muscle, aim for a calorie deficit in the same way but up your protein to 1-2g of protein per kg of body weight.

✅ Take the weekend off.  (see Understanding Intermittent Fasting).   The greatest predictor of any diet is adherence, and taking a cheat day or the weekend off makes diets more practical, more enjoyable and essentially more sustainable.

 

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