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A protein smoothie helps weight loss when it takes the place of a meal and holds you until the next one. Drunk on top of your usual breakfast, or made mostly of fruit, honey and juice, it adds weight instead. Studies from Purdue and Penn State found that the body registers calories from drinks less well than calories from solid food. A useful weight loss smoothie is therefore thick, carries 20–30 g of protein and some fibre, uses whole fruit, and lands at roughly 300–400 calories.
Blend a protein base such as hung curd, sattu, paneer or a protein powder with one portion of fruit and a spoon of oats or seeds. Use water, toned milk or soya milk as the liquid. Leave out sugar, honey and packaged juice, and drink it in place of a meal.
Can a protein smoothie help you lose weight?
Used to replace a meal, a shake or smoothie has decent evidence behind it. Nerys Astbury's team at Oxford reviewed 23 trials with 7,884 adults that compared programmes using meal replacements with other diets. After a year, people on a meal replacement plan with support had lost about 2.2 kg more than those on other diets with the same support. With extra support the difference was larger.
Those trials mostly used ready-made shakes with a fixed amount of protein and calories. A home smoothie can do the same job if you make it the same way each time and it truly replaces a meal. A fixed portion at breakfast, the meal many people skip or grab on the move, seems to be a large part of why they help.
As an addition, a smoothie can easily add weight. A glass of banana, mango, full-fat milk, honey and a scoop of powder can reach the calories of a full lunch. Drunk alongside breakfast rather than instead of it, it simply raises the day's total.
Sources: [1]
Why do drinks fill you up less than food?
Richard Mattes and Wayne Campbell at Purdue gave adults the same 300 calories of apple as a whole fruit, as apple sauce and as juice. The whole apple suppressed hunger most, the sauce came next, and the juice did least. People also got hungry again sooner after the juice.
Julie Flood-Obbagy and Barbara Rolls at Penn State ran a similar test before lunch. Eating a whole apple first cut the calories eaten at that meal by 15% compared with eating nothing first. Apple sauce and apple juice did not reduce lunch as much, even with fibre added back to the juice.
An older Purdue study by DiMeglio and Mattes went further. Volunteers took 450 extra calories a day for four weeks, once as jelly beans and once as a soft drink. With the solid sweets they ate less of everything else and their weight held. With the drink they did not cut back at all, and their weight went up.
How do you make a smoothie more filling?
Thickness is the first fix. A smoothie you can drink in thirty seconds behaves more like juice; one that needs a spoon, or ten minutes of sipping, behaves more like a meal. Pouring it into a bowl and topping it with a few seeds slows most people down. Keep the fruit whole and blended with its pulp, which is closer to the apple sauce in the Penn State test than to the juice.
Fibre adds bulk without much energy. Two tablespoons of rolled oats bring about 60 calories, and a teaspoon of soaked chia or flax seeds about 20. A handful of spinach, half a cucumber, ice and water cost almost nothing and make the glass bigger.
Then there is protein. Heather Leidy's review of the research found that higher-protein meals reliably make people feel fuller, even if the effect on the next meal is modest. Drink the smoothie sitting down, at the table, rather than in the car on the way to work.
How much protein should a weight loss smoothie have?
Aim for roughly 20–30 g if the smoothie is a meal, a common amount for a single meal in the higher-protein diets Leidy's review describes. For calories, most women eating 1,200–1,500 a day under the usual American guideline can fit a 300–400 calorie smoothie at breakfast and still eat two proper meals.
You can reach the protein without powder. Hung curd carries roughly twice the protein of ordinary curd, and sattu, soft paneer, firm tofu and soya milk all add more; combining two of them usually gets close to 20 g. If you do buy a powder, check the label for protein per scoop, usually 20–25 g, calories under about 130, and little or no added sugar. Whey suits most people who digest milk well, and pea or soy blends suit those who do not.
Robert Morton's meta-analysis of 49 trials found that protein supplements improved the muscle gained from resistance training. The benefit flattened once total protein passed about 1.6 g per kg of body weight a day.
Which four Indian smoothie recipes work for weight loss?
Each recipe makes one glass for one meal. The protein and calorie figures are approximate, from typical label values, and they shift with the brand of curd, paneer or powder you use.
Sattu and banana: 3 tablespoons of sattu, half a small banana, 150 g of hung curd, a pinch of roasted jeera and 200 ml of cold water. About 20 g of protein and 320 calories. It is thick and slightly savoury, and a good summer breakfast.
Papaya and hung curd: a cup of ripe papaya, 200 g of hung curd, a tablespoon of rolled oats, a squeeze of lemon and some ice. About 18–20 g of protein and 300 calories. The papaya brings enough sweetness that no sugar is needed.
Green chaas smoothie: a handful of spinach, half a cucumber, mint, 200 g of regular curd and 75 g of soft paneer, with rock salt, roasted jeera, ice and water. About 20 g of protein and 330 calories, for people who dislike sweet breakfasts.
Cocoa, oats and whey: one scoop of whey or plant protein, a tablespoon of unsweetened cocoa, two tablespoons of oats, a teaspoon of soaked chia and 250 ml of toned milk. About 35 g of protein and 360 calories; unsweetened soya milk brings it nearer 300. Pour it into a bowl, add a few chopped almonds and eat it with a spoon.
Sources: [5]
What should you leave out of a weight loss smoothie?
Sugar, honey and jaggery come first, because they turn a meal into a dessert. Packaged fruit juice is next. Fumiaki Imamura's meta-analysis of 17 cohorts linked regular fruit juice drinking with a modestly higher risk of type 2 diabetes. Sugar-sweetened drinks carried a clearer risk, and some of it held even after allowing for body weight.
Ice cream, full-cream milk with malai, dates by the handful and two bananas instead of half all push the calories up quickly. A large mango smoothie with milk can easily equal a plate of rice, dal and sabzi in energy while filling you for a fraction of the time.
Watch the extras sold as healthy too. Granola, sweetened nut butters and flavoured yoghurts often carry added sugar. Read the label, and keep any sweetness to the fruit itself.
Sources: [7]
Why does the protein in your smoothie protect muscle while you lose weight?
When you eat less, the body takes part of the lost weight from muscle. Thomas Wycherley, a nutrition researcher in Adelaide, pooled 24 trials in which people ate the same calories with either more or less protein. Over about three months the higher-protein groups lost slightly more fat and kept about 0.43 kg more lean mass.
Half a kilo matters because of what muscle does. Muscle burns energy at rest, soaks up blood sugar after meals and makes the stairs easier as you get lighter. A protein smoothie at breakfast, dal, paneer, eggs or chicken at the other meals, and two strength sessions a week each add to that.
Metaboliq's doctor-led plans are set up around the same idea, aiming to lose up to 20% of body weight while keeping muscle, with a protein target for each person. They begin with a home blood test and a doctor's review. Kidney function and blood sugar decide how much protein and how much fruit suit each person.
Sources: [8]